A pacemaker (or artificial pacemaker, so as not to be confused with the heart's natural pacemaker) is a medical device which uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart. The primary purpose of a pacemaker is to maintain an adequate heart rate, either because the heart's native pacemaker is not fast enough, or there is a block in the heart's electrical conduction system. Modern pacemakers are externally programmable and allow the cardiologist to select the optimum pacing modes for individual patients. Some combine a pacemaker and implantable defibrillator in a single implantable device. Others have multiple electrodes stimulating differing positions within the heart to improve synchronisation of the lower chambers of the heart.
Epicardial pacing wires are routine leads used for temporary cardiac pacing after heart surgery. During surgery the heart is subjected to stress which can lead to myocardial ischemia and cardiac depression. Temporary pacing may be necessary to re-establish electrical conduction. Atrial wires (A wires) are positioned on the right atrial surface and exit the chest wall to the right of the sternum. Atrial wires are attached via a connecting cable to “A” marked terminals on the pacemaker box. Ventricular wires (V wires) are positioned on the right ventricular surface and exit the chest wall to the left of the sternum. Ventricular wires are attached via connecting cable to “V” marked terminals on the pacemaker box. Epicardial pacing after heart surgery allows for the treatment of dysrhythmias, the improvement of haemodynamic functioning, and to maintain backup rate.
Cardiac Resynchronization Therapy (CRT):
A dual chamber (sequential) pacemaker, also known as cardiac resynchronization therapy (CRT) is a type of pacemaker that can pace both ventricles (right and left) of the heart. By pacing both sides of the heart, the pacemaker can resynchronize a heart that does not beat in synchrony, which is common in heart failure patients. CRT devices have three leads, one in the atrium, one in the right ventricle, and a final one is inserted through the coronary sinus to pace the left ventricle. CRT devices are shown to reduce mortality and improve quality of life in groups of heart failure patients.
Advancements in pacemaker function.
When first invented, pacemakers controlled only the rate at which the heart's two largest chambers, the ventricles, beat. Many advancements, have been made to enhance the control of the pacemaker once implanted. Many of these enhancements have been made possible by the transition to microprocessor controlled pacemakers. Pacemakers that control not only the ventricles but the atria as well have become common. Pacemakers that control both the atria and ventricles are called dual-chamber pacemakers. Although these dual-chamber models are usually more expensive, timing the contractions of the atria to precede that of the ventricles improves the pumping efficiency of the heart and can be useful in congestive heart failure. Rate responsive pacing allows the device to sense the physical activity of the patient and respond appropriately by increasing or decreasing the base pacing rate via rate response algorithms. Trials have shown that unnecessary pacing of the right ventricle can lead to heart failure. New devices can keep the amount of right ventricle pacing to a minimum and thus prevent worsening of the heart disease. Another advancement in pacemaker technology is left ventricular pacing. A pacemaker wire is placed on the outer surface of the left ventricle, with the goal of more physiological pacing than available in standard pacemakers. The extra wire is implanted to improve symptoms in patients with severe heart failure.
Rapid and forceful contraction of the heart of which the patient is conscious.
Paralysis is the complete loss of muscle function for one or more muscle groups. Paralysis often includes loss of feeling in the affected area.
Muscle relaxant drugs block neuromuscular transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles.
Parasympathetic nervous system.
The parasympathetic nervous system (PNS) is one of three divisions of the autonomic nervous system (ANS). The ANS is subdivided into the sympathetic (SNS), parasympathetic (PNS) and enteric (bowels) nervous system (ENS). Sympathetic and parasympathetic divisions typically function in opposition to each other. But this opposition is better termed complementary in nature rather than antagonistic. For an analogy, one may think of the sympathetic division as the accelerator and the parasympathetic division as the brake. The sympathetic division typically functions in actions requiring quick responses. The parasympathetic division functions with actions that do not require immediate reaction.
An uncontrollable outburst, a sudden attack or recurrence of a disease.
Patient-controlled analgesia (PCA):
Patient-controlled analgesia (PCA) is any method of allowing a person in pain to administer their own pain relief.
General use: The most common form of this is the paracetamol that many keep in their bathroom cabinet. If a complaint, e.g. a headache, does not resolve with a small dose of painkiller then more may be taken up to a maximum dose. This situation has the patient in control, and is in fact the most common patient-controlled analgesia. As pain is a combination of tissue damage and emotional state, being in control means reducing the emotional component of pain.
Hospital use: PCA has passed into medical jargon to mean the electronically controlled infusion pump that delivers a prescribed amount of intravenous or epidural analgesic to the patient when he or she activates a button. Opioids are the medication most often administered through PCAs. PCA was introduced by Dr. Philip H. Sechzer in the later 1960s and described in 1971.
Among the benefits of this device are:
• It saves time between when the patient feels pain and/or the need to receive analgesia and when it is administered (activation automatically pumps the dose into a pre- existing IV line into the patient).
• It reduces workload of the nursing staff (an amount of the prescribed analgesic is pre-loaded into the PCA, enough for multiple doses).
• It reduces the chances for medication errors (the PCA is programmed per the physician's order for amount and interval between doses and "locks out" the patient if he or she attempts to self- administer too often.)
• Patients who use PCAs report better analgesia and lower pain scores than those patients who have to request analgesia from the nursing staff when they are in pain.
• PCA provides a measurement of how much pain an individual patient is experiencing from one day to the next.
• It involves patients in their own care, giving them control and ultimately rendering better patient outcomes
Patient-controlled analgesia (PCA)(cont).
• Patients may be unwilling to use the PCA or be physically or mentally unable to. (in a lot of cases physical inability can be mitigated through use of a eye gaze, sip-puff or alternative switch access method. PCA pumps are rated among the worlds most accessible pieces of equipment since all manufacturers must have alternative switch access built into their PCA pumps.
• The pumps are often expensive and may malfunction. (malfunctions are usually limited though and a lot of malfunctions result from an improperly maintained/charged battery.)
• More importantly, the dosing regimen may be set so that the patient does not receive enough analgesia (bolus doses set too small, lock-out too long). When the patient sleeps, the analgesic wears off so they wake in pain. This is sometimes countered by setting a background continuous infusion of the analgesia.
Patient-controlled epidural analgesia (PCEA) is a related term describing the patient-controlled administration of analgesic medicine in the epidural space, by way of intermittent boluses or infusion pumps. This is most commonly used by terminally ill cancer patients.
A pathogen or infectious agent is a biological agent that causes disease or illness to its host. The term is most often used for agents that disrupt the normal physiology of a multicellular animal or plant. However, pathogens can infect unicellular organisms from all of the biological kingdoms. The term pathogen is derived from the Greek παθογένεια, "that which produces suffering." There are several substrates and pathways where by pathogens can invade a host; the principal pathways have different episodic time frames, but soil contamination has the longest or most persistent potential for harboring a pathogen.
The body contains many natural defenses against some of the common pathogens (such as Pneumocystis) in the form of the human immune system and by some "helpful" bacteria present in the human body's normal flora. However, if the immune system or "good" bacteria is damaged in any way (such as by chemotherapy, human immunodeficiency virus (HIV), or antibiotics being taken to kill other pathogens), pathogenic bacteria that were being held at bay can proliferate and cause harm to the host. Such cases are called opportunistic infections.
Some pathogens (such as the bacterium Yersinia pestis, which may have caused the Black Plague, and the Variola virus) have been found to be responsible for massive amounts of casualties and have had numerous effects on afflicted groups. Of particular note in modern times is HIV, which is known to have infected several million humans globally, as well as Severe Acute Respiratory Syndrome (SARS) and the Influenza virus. Today, while many medical advances have been made to safeguard against infection by pathogens, through the use of vaccination, antibiotics, and fungicide, pathogens continue to threaten human life. Social advances such as food safety, hygiene, and water treatment have reduced the threat from some pathogens.
Peptides (from the Greek πεπτος, "digestible") are the family of short molecules formed from the linking, in a defined order, of various α-amino acids. The link between one amino acid residue and the next is an amide bond and is sometimes referred to as a peptide bond.
Perfusion (Physiology): Perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. Perfusion ("F") can be measured with the following formula, where Pa is mean arterial pressure, Pv is mean venous pressure, and R is vascular resistance.
The terms "perfusion" and "perfusion pressure" are sometimes used inter-changably, but the equation should make clear that resistance can have an effect on the perfusion, but not on the perfusion pressure. The terms "over-perfusion" and "under-perfusion" are measured relative to the average level of perfusion across all tissues in an individual body, and the terms should not be confused with hypo-perfusion and "hyper-perfusion", which measure the perfusion level to the tissue's current need.
Tissues like the skin are considered over-perfused and receive more blood than would be expected to meet the metabolic needs of the tissue. In the case of the skin, extra blood flow is used for thermoregulation. In addition to delivering oxygen, the blood helps dissipate heat by redirecting warm blood close to the surface where it can cool the body through the sweating and thermal radiation.
Pericarditis is an inflammation of the pericardium (the fibrous sac surrounding the heart). Pericarditis is further classified according to the composition of the inflammatory exudate – (a substance that oozes out): serous – (an amber, watery fluid), purulent – (containing, consisting of, or being pus), fibrinous – (characterized by the presence of fibrin), and haemorrhagic – (a copious discharge of blood) types are distinguished (images).
Acute pericarditis is more common than chronic pericarditis, and can occur as a complication of infections, immunologic conditions, or heart attack.
Chest pain, radiating to the back and relieved by sitting up forward and worsened by lying down, is the classical presentation. Other symptoms of pericarditis may include dry cough, fever, fatigue and anxiety. Pericarditis can be misdiagnosed as myocardial infarction, and vice versa.
The classic sign of pericarditis is a friction rub. Other signs include ST-elevation and PR-depression on ECG (all leads); cardiac tamponade (pulsus paradoxus (see below) with hypotension), and congestive heart failure (elevated jugular venous pressure with peripheral oedema).
In medicine, a pulsus paradoxus (PP), also paradoxic pulse and paradoxical pulse, is an exaggeration of the normal variation in the pulse during the inspiratory phase of respiration, in which the pulse becomes weaker as one inhales and stronger as one exhales. It is a sign that is indicative of several conditions including cardiac tamponade and lung diseases (e.g. asthma, COPD).
The pericardium is a double-walled sac that contains the heart and the roots of the great vessels. There are two layers to this sac: the fibrous pericardium and the serous pericardium. The serous pericardium, in turn, is divided into two layers; in between these two layers there is a potential space called the pericardial cavity.
Generally, a periphery is a boundary or outer part of any space or body. It is derived from the Greek word περιφέρεια, meaning a circumference or outer surface. In biology, the periphery of the body is the part that is away from the central or core regions.
Peripheral nervous system. (P.N.S).
The Peripheral nervous system, or PNS, is part of the nervous system, and consists of the nerves and neurons that reside or extend outside the central nervous system (the brain and spinal cord) to serve the limbs and organs, for example. Unlike the central nervous system, however, the PNS is not protected by bone, leaving it exposed to toxins and mechanical injuries. The peripheral nervous system is divided into the somatic nervous system-( the term somatic refers to the body, the word comes from the Greek word Σωματικóς (Somatikòs), meaning "of the body" ) and the autonomic nervous system.
The somatic nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements through the action of skeletal muscles, and with reception of external stimuli, which helps keep the body in touch with its surroundings (e.g., touch, hearing, and sight).
The autonomic nervous system (ANS) (or visceral nervous system) is the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body. These maintenance activities are primarily performed without conscious control or sensation. The ANS has far reaching effects, including: heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition - (the discharge of urine), and erection. Whereas most of its actions are involuntary, some ANS functions work in tandem with the conscious mind, such as breathing. Its main components are its sensory system, motor system (comprised of the parasympathetic nervous system and sympathetic nervous system), and the enteric nervous system. The enteric nervous system (ENS) is the part of the nervous system that directly controls the gastrointestinal system.
Purkinje fibers (or Purkyne tissue) are located in the inner ventricular walls of the heart, just beneath the endocardium. These fibers are specialized myocardial fibers that conduct an electrical stimulus or impulse that enables the heart to contract in a coordinated fashion. Purkinje fibers work with the sinoatrial node (SA node) and the atrioventricular node (AV node) to control the heart rate.
The pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial, or superior, to the oesophagus, larynx, and trachea.
pH /potenz Hydrogen .
This is a rough measure the acidity of a solution. The "p" stands for "potenz" (this means the potential to be) and the "H" stands for Hydrogen. The pH of distilled water is 7, this is neutral. Any solution with a pH below 7 (i.e. pH 1.0 to pH 6.9) is an acid and any solution with a pH above 7 (i.e. pH 7.1 to pH 14) is an alkali.
Acidic solutions have a pH between 1 and 6.9 === your stomach contains HCl it is pH2.
Alkaline solutions have a pH between 7.1 and 14. === your small intestine is pH 9.
Neutral solutions are neither acidic nor alkaline so their pH is 7.
Phenethylamine, is an alkaloid and monoamine-(containing one amino group). In the human brain, it is believed to function as a neuro-modulator or neurotransmitter (trace amine).
Phlebitis is an inflammation of a vein, usually in the legs. When phlebitis is associated with the formation of blood clots (thrombosis), usually in the deep veins of the legs, the condition is called thrombophlebitis.
Technically, a phosphodiesterase is any enzyme that breaks a phosphodiester bond. Usually, people speaking of phosphodiesterase are referring to cyclic nucleotide-( see nucleoside) phosphodiesterases which have great clinical significance. However, many other enzyme families are technically phosphodiesterases including phospholipases C and D, autotaxin, sphingomyelin phosphodiesterase, DNAses, RNAses, and restriction endo-nucleases (which all break the phosphodiester backbone of DNA or RNA) as well as numerous less-well-characterized small-molecule phosphodiesterases. The cyclic nucleotide phosphodiesterases (PDE) comprise a group of enzymes that degrade the phosphodiester bond in the second messenger molecules Cyclic adenosine monophosphate (cAMP) and Cyclic guanosine monophosphate ( cGMP ). They regulate the localization, duration, and amplitude of cyclic nucleotide signaling within sub-cellular domains. PDEs are therefore important regulators of signal transduction mediated by these second messenger molecules.
Pulse Initiated Continuous Cardiac Output (PICO) system which can derive cardiac output from the arterial waveform without the need for an independent method of calibration. Hence continuous cardiac output can be measured directly from a conventional arterial line. This method has yet to be extensively evaluated, but early studies suggest that it is accurate.
Blood plasma is the liquid component of blood, in which the blood cells are suspended. Plasma is a yellow colored liquid. Plasma is the largest single component of blood, making up about 55% of total blood volume. Blood plasma contains many vital proteins including fibrinogen, globulins-(is one of the two types of serum proteins, the other being albumin), and human serum albumin. Sometimes blood plasma may contain viral impurities which must be extracted through viral processing. A simple way to separate plasma from blood cells in a blood sample is by centrifugation. "Serum" refers to blood plasma in which clotting factors (such as fibrin) have been removed naturally by allowing the blood to clot prior to isolating the liquid component. Plasma resembles whey in appearance (transparent with a faint straw color). It is mainly composed of water, blood proteins, and inorganic electrolytes. It serves as transport medium for glucose, lipids-(fat-soluble), amino acids, hormones, metabolic end products, carbon dioxide (CO2) and oxygen (O2). The oxygen transport capacity and oxygen content of plasma is much lower than that of the haemoglobin in red blood cells; the CO2 will, however, increase under hyperbaric-(higher than atmospheric pressure) conditions. Plasma is the storage and transport medium of clotting factors. Its protein content is necessary to maintain the oncotic pressure-( see below)of the blood, which "holds" the serum within the vessels. Oncotic pressure: In blood plasma, the dissolved compounds have an osmotic pressure. The difference between the osmotic pressure exerted by plasma proteins (colloidal osmotic pressure) in blood plasma and that exerted by tissue fluid proteins is called the oncotic pressure.
Plasma expanders are used to restore the circulating volume of a hypovolaemic patient. Typically, colloids are used to expand the plasma volume, although combinations of hypertonic-(a solution of higher osmotic pressure than another solution) crystalloid and colloid have recently been used. The currently available colloids vary in their physico-chemical, pharmaco-dynamic and pharmaco-kinetic properties. In particular, they differ in molecular weight, which partly determines their duration of action, and in their ability to expand the plasma volume. Dextran, starches and hypertonic colloid solutions improve oxygen flux within the microcirculation. Despite their benefits, the use of dextran and high molecular weight starches is limited by their negative impact on coagulation. In addition, these macro-molecules may also induce acute renal failure in susceptible patients. Current research focuses on the development of artificial oxygen-carriers as plasma expanders.
The cell membrane (also called the plasma membrane) is a semi-permeable lipid-(fat-soluble) bi-layer common to all living cells.
Plasmin is an important enzyme present in blood that degrades many blood plasma proteins, most notably fibrin clots. The degradation of fibrin is termed fibrinolysis. It is a serine protease that is released as plasminogen into the circulation and activated by tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), thrombin, fibrin and factor XII (Hageman factor). It is inactived by alpha 2-antiplasmin, a serine protease inhibitor (serpin).
Plasminogen activator inhibitor-1 is the principal inhibitor of tissue plasminogen activator (tPA) and urokinase (uPA), the activators of plasminogen and hence fibrinolysis (the physiological breakdown of blood clots). It is a serine protease inhibitor (serpin) protein (SERPINE1).
The other PAI, plasminogen activator inhibitor-2 (PAI-2) is secreted by the placenta and only present in significant amounts during pregnancy. In addition, protease nexin acts as an inhibitor of tPA and urokinase. PAI-1, however, is the main inhibitor of the plasminogen activators.
Platelets or thrombocytes are the cell fragments circulating in the blood that are involved in the cellular mechanisms of primary haemostasis leading to the formation of blood clots. Dysfunction or low levels of platelets predisposes to bleeding, while high levels, although usually asymptomatic, may increase the risk of thrombosis. Technology uses a centrifuge to separate out the patients own blood components by their various densities. The red blood cells (RBCs) are denser and will move to the bottom. The plasma fraction is the least dense and will float on the top layer. The “buffy coat” which contains the majority of platelets will be sandwiched between the plasma and above the RBCs. Platelet concentrate is obtained by the process of spinning down the patient’s own blood and collecting the buffy coat which contains the concentrated platelets and white blood cells.
A normal platelet count in a healthy person is between 150,000 and 400,000 per mm³ of blood (150–400 x 109/L). 95% of healthy people will have platelet counts in this range. Some will have statistically abnormal platelet counts while having no abnormality, although the likelihood increases if the platelet count is either very low or very high. Both thrombocytopenia- (few platelets in blood) and thrombocytosis- (high counts), may present with coagulation problems. Generally, low platelet counts increase bleeding risks.
Low platelet counts are generally not corrected by transfusion unless the patient is bleeding or the count has fallen below 5 x 109/L. In patients having surgery, a level below 50 x 109/L) is associated with abnormal surgical bleeding, and regional anaesthetic procedures such as epidurals are avoided for levels below 80-100.
Normal platelet counts are not a guarantee of adequate function. In some states the platelets, while being adequate in number, are dysfunctional. For instance, aspirin irreversibly disrupts platelet function, and hence normal haemostasis; normal platelet function may not return until the aspirin has ceased and all the affected platelets have been replaced by new ones, which can take over a week.
A deposit of fatty material on the inner lining of an arterial wall, characteristic of atherosclerosis.
The lungs are surrounded by two membranes, the pleurae. The outer pleura is attached to the chest wall and is known as the parietal pleura; the inner one is attached to the lung and other visceral-(pertaining to the internal organs ) tissues and is known as the visceral pleura. In between the two is an actual thin space known as the pleural cavity or pleural space. It is filled with pleural fluid, a serous fluid produced by the pleura. A normal 70 kg human has approximately 12-15 mL of pleural fluid.
Pleural effusion is excess fluid that accumulates in the pleural cavity, the fluid-filled space that surrounds the lungs.
Four types of fluids can accumulate in the pleural space:
• Serous fluid (hydrothorax), the term serous fluid is used for various bodily fluids that are typically pale yellow and transparent.
• Blood (haemothorax)
• Chyle (chylothorax)
• Pus (pyothorax or empyema)
A hydrothorax is a condition that results from fluid accumulating in the pleural cavity. In haemothorax this fluid is blood (as in major chest injuries), in pyothorax the fluid is pus (resulting from chest infections), in chylothorax it is lymph fluid (resulting from rupture of the thoracic duct).
A pneumothorax is a condition where air enters the lining of the lung causing the chest wall and lungs to pull away from each other causing the lung to collapse. The most common reason for having a pleurectomy is a collapsed lung (pneumothorax) that keeps recurring. Pneumothorax is common in young people particularly males who are of tall thin physique and older adults with lung problems.
They can occur for a variety of reasons including trauma to the chest from a fall or accident. Symptoms are breathlessness and pain in the chest area.
Another reason a pleurectomy is performed is because of recurrent fluid on the lungs known as a pleural effusion. A pleurectomy involves removing the lining between the lung and the chest wall. This causes the surface of the lung to stick to the chest wall, preventing further collapse. A thoracotomy is performed on the affected side. This will enable the surgeon to access the lung through the rib cage at the back. In order to help the lung go back up after the procedure the surgeon will insert one or two chest drains. These drains allow air to escape in order for your lung to expand.
A pneumonectomy is an surgical procedure to remove all or part of a lung. Removal of just one lobe of the lung is specifically referred to as a lobectomy, and that of a segment of the lung as a segmentectomy. The most common cause for a pneumonectomy is to excise tumourous tissue arising from lung cancer. Other indications for lobectomy include a solitary pulmonary nodule (the possibility of undiagnosed small-cell cancer in this instance is not necessarily a reason for avoiding thoracotomy), or bronchiectasis-( see below ) where other forms of treatment have failed, particularly if it is localised and recurrent haemoptysis-( see below ) is present. In the days prior to the use of antibiotics in tuberculosis treatment, tuberculosis was sometimes treated surgically by pneumonectomy.
It is clear that the operation will reduce the respiratory capacity of the patient; before conducting a pneumonectomy, the surgeon will evaluate the ability of the patient to function after the lung tissue is removed. After the operation, patients are often given an incentive spirometer to help exercise their remaining lung and to improve breathing function. A rib or two is sometimes removed to allow the surgeon better access to the lung.
There are two types of pneumonectomy:
1. Simple pneumonectomy: removal of just the affected lung
2. Extrapleural pneumonectomy: removal of the affected lung, plus part of the diaphragm and the pericardium (lining of the heart) on that side.
Bronchiectasis is a disease that causes localized, irreversible dilatation of part of the bronchial tree. Involved bronchi are dilated, inflamed, and easily collapsible, resulting in airflow obstruction and impaired clearance of secretions. Bronchiectasis is associated with a wide range of disorders, but it usually results from necrotizing bacterial infections, such as infections caused by the Staphylococcus or Klebsiella species or Bordetella pertussis.
Haemoptysis is the expectoration (coughing up) of blood or of blood-stained sputum from the bronchi, larynx, trachea, or lungs (e.g. in tuberculosis or other respiratory infections).It is not the same as haematemesis, which refers to vomiting up blood.
Pneumonia is an illness of the lungs and respiratory system in which the alveoli (microscopic air-filled sacs of the lung responsible for absorbing oxygen from the atmosphere) become inflamed and flooded with fluid. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites, and chemical or physical injury to the lungs. Typical symptoms associated with pneumonia include cough, chest pain, fever, and difficulty in breathing. Diagnostic tools include x-rays and examination of the sputum. Treatment depends on the cause of pneumonia; bacterial pneumonia is treated with antibiotics. Pneumonia is a common illness which occurs in all age groups,
and is a leading cause of death among the elderly and people who are chronically and terminally ill. Vaccines to prevent certain types of pneumonia are available. The prognosis depends on the type of pneumonia, the appropriate treatment, any complications, and the person's underlying health.
In medicine (pulmonology), a pneumothorax, or collapsed lung, is a potential medical emergency caused by accumulation of air or gas in the pleural cavity, occurring as a result of disease or injury.
It can result from:
• A penetrating chest wound
• Baro-trauma to the lungs: is physical damage to body tissues caused by a difference in pressure between an air space inside or beside the body and the surrounding gas or liquid.
• Spontaneously (most commonly in tall slim young males and in Marfan syndrome, a genetic disorder of the connective tissue characterized by disproportionately long limbs, long thin fingers, a relatively tall stature, and a predisposition to cardiovascular abnormalities, specifically those affecting the heart valves and aorta).
• Chronic lung pathologies including emphysema, asthma
• Acute infections
• Chronic infections, such as tuberculosis
Pneumothoraces are divided into tension and non-tension pneumathoraces. A tension pneumothorax is a medical emergency as air accumulates in the pleural space with each breath. The remorseless increase in intrathoracic pressure results in massive shifts of the mediastinum away from the affected lung compressing intrathoracic vessels. A non-tension pneumothorax by contrast is a less severe pathology because there is no ongoing accumulation of air and hence no increasing pressure on the organs within the chest.
The accumulation of blood in the thoracic cavity (heamothorax) exacerbates the problem, creating a pneumohaemothorax.
Polarity, is a concept in chemistry which describes how equally bonding electrons are shared between atoms. For example, water is thought to be polar because of the uneven sharing of its electrons. However, methane is considered non-polar because the carbon shares the hydrogen molecules uniformally.
Porphyrias are a group of inherited or acquired disorders of certain enzymes in the haem biosynthetic pathway (also called porphyrin pathway). They are broadly classified as hepatic porphyrias or erythropoietic porphyrias, based on the site of the overproduction and mainly accumulation of the porphyrins (or their chemical precursors). They manifest with either skin problems or with neurological complications (or occasionally both). The term derives from the Greek πορφύρα, porphura, meaning "purple pigment".
Post-infarction ventricular septal defect / rupture.
One of the most devastating complications of myocardial infarction is post-infarction ventricular septal rupture. The incidence is approximately 1-2% after acute myocardial infarction. The majority of cases involve the anteroapical - (Latin antero; before, apical - of, at, or forming the apex) septum -(a dividing wall, membrane) secondary to occlusion of the left anterior descending artery – (see coronary artery bypass surgery). In the minority, occlusion of a dominant right coronary artery – (see coronary artery bypass surgery). or a dominant left circumflex artery– (see coronary artery bypass surgery) feeding the posterior descending artery– (see coronary artery bypass surgery) results in posterior septal rupture. Patients are usually discovered to have a loud holosystolic - (relating to or lasting throughout the systole of a heartbeat) murmur - (an abnormal sound heard on listening to the heart) in association with clinical deterioration and right-sided heart failure 2-5 days post-infarction.
There are two standard methods of repair. The first involves using a prosthetic or pericardial patch to cover the defect by suturing the patch circumferentially to the septum. The two major drawbacks of this method are that a) the sutures may be placed through ischemic, friable muscle and tear, and b) the ventriculotomy-(Incision into a ventricle of the brain or heart) (which is usually made through the zone of infarct) is subject to LV systolic pressures after surgery.
To avoid these potential problems, a method of infarct exclusion that creates a neo-left ventricle using a pericardial patch. The septal defect, septal infarction, and free wall infarction (if present) are all excluded from the high pressures of the left ventricle.
A transesophageal echocardiogram probe should be available so the repair can be inspected upon completion. The patient is given general anesthesia and prepped and draped in the standard fashion. A median sternotomy is performed and if concomitant coronary artery bypass is planned, the internal mammary artery may be dissected at this point. Otherwise, the pericardium is opened and the heart inspected for evidence of transmural - (passing through a wall, as of the body or or any hollow structure) infarction. Single or double venous cannulation can be used, with standard aortic cannulation and full cardiopulmonary bypass.
An anterolateral- (Latin antero; before, apical - of, at, or forming the apex) left ventriculotomy-(Incision into a ventricle of the brain or heart) is made through the area of infarction parallel to and two centimeters away from the left anterior descending artery. Stay sutures can be placed through the edges of the ventriculotomy to maintain an open visual field. The inter-ventricular septum, area of infarction.
Tips and Pitfalls
• All sutures along the septum must be placed into healthy, non-ischaemic muscle to avoid the complication of suture line breakdown and a recurrent defect.
• If the muscle along the septum is thin, interrupted sutures with Teflon pledgets may create a stronger repair that will not unravel if one suture erodes through friable muscle.
• Direct closure of the septal defect prior to patch on-lay adds no strength to the repair and distorts the natural geometry of the left ventricle.
Post-infarction ventricular septal defect / rupture (cont).
• Incising the left ventricle through the area of infarction, and then suturing the patch beyond
• the infarctotomy, excludes both the defect and the infarction from high left sided pressures.
• Concomitant coronary artery bypass grafting, as it has been shown to improve long-term survival after post-infarction ventricular septal rupture.
• Redundancy of the patch is key as the sutures hold the patch in place, buttressed by the septum. If the patch is stretched taut excessive stress on the sutures might pull them through the fragile muscle.
Pertaining to the area on the distal side of a synaptic cleft.
In cell biology, potassium channels are the most common type of ion channel. They form potassium-selective pores that span cell membranes. Potassium channels are found in most cells and control cell function.
In cardiac physiology, preload is the pressure stretching the ventricle of the heart, after passive filling and atrial contraction. If the chamber is not mentioned, it is usually assumed to be the left ventricle.
Preload is theoretically most accurately described as the initial stretching of a single cardiac myocyte prior to contraction. This cannot be measured in vivo - (Latin: (with)in the living) and therefore other measurements are used as estimates. Estimation is inaccurate, for example in a chronically dilated ventricle new sarcomeres - (is the basic unit of a muscle's cross-striated myofibril - (are cylindrical organelles, found within muscle cells). may have formed in the heart muscle allowing the relaxed ventricle to appear enlarged. The term end-diastolic volume is better suited to the clinic, although not exactly equivalent to the laboratory term preload.
Premedication refers to a drug treatment given to a patient before a (surgical or invasive) medical procedure. These drugs are typically sedative or analgesic.
Situated in front of or occurring before a synapse: a pre-synaptic nerve fibre; a pre-synaptic stimulus.
Prothrombin (see I.N.R).
Thrombin (activated Factor II) is a coagulation protein that has many effects in the coagulation cascade. It is a serine protease that converts soluble fibrinogen into insoluble strands of fibrin, as well as catalyzing many other coagulation-related reactions. The prothrombin gene is located on the eleventh chromosome The molecular weight of prothrombin is approximately 72000. Once activated, the catalytic domain of prothrombin (i.e. thrombin, molecular weight 36000) is released from prothrombin fragment 1.2. Thrombin converts fibrinogen to an active form that assembles into fibrin. Thrombin also activates factor XI, factor V and factor VIII. This positive feedback accelerates the production of thrombin. Activation of prothrombin is crucial in physiological and pathological coagulation. Various rare diseases involving prothrombin have been described (e.g. hypoprothrombinemia- is a blood disorder in which a deficiency of prothrombin (Factor II) results in impaired blood clotting, leading to an increased physiological risk for bleeding).
Related to the lung often begin with pulmo-, from the Latin pulmonarius ("of the lungs"), or with pneumo- (from Greek πνεύμω "lung").
In medicine, a person's pulse is the throbbing of their arteries as an effect of the heart beat. It can be felt at the neck (carotid artery), at the wrist (radial artery), behind the knee (Popliteal artery), on the inside of the elbow (Brachial artery), near the ankle joint (Posterior Tibial artery), and a few other places. Pressure waves move the artery walls, which are pliable; these waves are not caused by the forward movement of the blood. When the heart contracts, blood is ejected into the aorta and the aorta stretches. At this point the wave of distention (pulse wave) is pronounced but relatively slow-moving (3 to 6 m/s). As it travels towards the peripheral blood vessels, it gradually diminishes and becomes faster. In the large arterial branches, its velocity is 7 to 10 m/s; in the small arteries, it is 15 to 35 m/s. The pressure pulse is transmitted 15 or more times more rapidly than the blood flow.
Pulseless ventricular tachycardia.
Pulseless VT is associated with no effective cardiac output, hence, no effective pulse, and is a cause of cardiac arrest. In this circumstance it is best treated the same way as ventricular fibrillation (VF) and is recognized as one of the shockable rhythms on the cardiac arrest protocol. Some VT is associated with reasonable cardiac output and may even be asymptomatic. The heart usually tolerates this rhythm poorly in the medium to long term, and patients may certainly deteriorate to pulseless VT or to VF.
Purine: One of the two classes of bases in DNA and RNA. The purine bases are guanine (G) and adenine (A). Uric acid, the offending substance in gout, is a purine end-product.
In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. Ligand-induced changes in the behavior of receptor proteins result in physiological changes that constitute the biological actions of the ligands.
Red Blood Cells (see erythrocytes).
Erythrocyte count or Red blood cell count.
An RBC count is a blood test that tells how many red blood cells (RBCs) you have. RBCs contain haemoglobin, which carries oxygen. How much oxygen your body tissues get depends on how many RBCs you have and how well they work.
Normal results vary, but in general the range is as follows:
• Male: 4.7 to 6.1 million cells per microliter (cells/mcL)
• Female: 4.2 to 5.4 million cells/mcL
Damaged RBCs do not live as long as normal. Injury inside the blood vessels, such as that caused by artificial heart valves or peripheral blood vessel disease, can damage RBCs.
Higher-than-normal numbers of RBCs may be due to:
Renal failure or kidney failure is the condition in which the kidneys fail to function adequately. Bio-chemically, it is typically detected by an elevated serum creatinine. In the science of physiology, renal failure is described as a decrease in the glomerular filtration rate. Glomerular filtration rate (GFR) is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman's capsule per unit time. Clinically, this is often measured to determine renal function. Compare to filtration fraction. Renal failure can broadly be divided into two categories (see flowchart below): acute renal failure and chronic renal failure.
Renal failure can broadly be divided into two categories: acute renal failure and chronic renal failure. The type of renal failure (acute vs. chronic) is determined by the trend in the serum creatinine. Other factors which may help differentiate acute and chronic renal failure include the presence of anaemia and the kidney size on ultrasound. Long-standing, i.e. chronic, renal failure generally leads to anaemia and small kidney size.
Acute renal failure:
Acute renal failure (ARF) is, as the name implies, a rapidly progressive loss of renal function, generally characterised by oliguria (decreased urine production, quantified as less than 400 mL per day in adults, less than 0.5 mL/kg/h in children or less than 1 mL/kg/h in infants); body water and body fluids disturbances; and electrolyte derangement. An underlying cause must be identified to arrest the progress, and dialysis may be necessary to bridge the time gap required for treating these fundamental causes. ARF can result from a large number of causes.
Chronic renal failure:
Chronic renal failure (CRF) can either develop slowly and show few initial symptoms, be the long term result of irreversible acute disease or be part of a disease progression. There are many causes of CRF. The most common cause is diabetes mellitus. End-stage renal failure (ESRF) is the ultimate consequence, in which case dialysis is required unless a donor for a renal transplant is found.
Acute on chronic renal failure
Acute renal failure can be present on top of chronic renal failure. This is called acute-on-chronic renal failure (AoCRF). The acute part of AoCRF may be reversible and the aim of treatment, as with ARF, is to return the patient to their baseline renal function, which is typically measured by serum creatinine. AoCRF, like ARF, can be difficult to distinguish from chronic renal failure, if the patient has not been monitored by a physician and no baseline (i.e., past) blood work is available for comparison.
Use of the term uremia
Before the advancement of modern medicine, renal failure was often referred to as uremic poisoning. Uremia was the term used to describe the contamination of the blood with urine. Starting around 1847, this term was used to describe reduced urine output, that was thought to be caused by the urine mixing with the blood instead of being voided through the urethra.
The concept of reperfusion has become so central to the modern treatment of acute myocardial infarction, that we are said to be in the reperfusion era. Patients who present with suspected acute myocardial infarction and ST segment elevation (STEMI) or new bundle branch block on the 12 lead ECG are presumed to have an occlusive thrombosis in an epicardial coronary artery. They are therefore candidates for immediate reperfusion, either with thrombolytic therapy, percutaneous coronary intervention (PCI) or when these therapies are unsuccessful, bypass surgery.
Respiratory arrest is the cessation of the normal tidal flow of the lungs due to paralysis of the diaphragm, collapse of the lung or any number of respiratory failures. It is a medical emergency and it usually is related to or coincides with a cardiac arrest. If respiratory arrest is prolonged, cardiac arrest quickly follows because progressive hypoxemia impairs cardiac function. Impending respiratory arrest is characterized by a depressed sensorium-(refers to the sum of an organism's perception, the "seat of sensation" where it experiences and interprets the environments within which it lives ) and feeble, gasping, or irregular respirations, often with accompanying tachycardia, diaphoresis-(excessive sweating), and relative hypertension due to agitation and CO2 accumulation.
Restenosis literally means the reoccurrence of stenosis. This is usually restenosis of an artery, or other blood vessel, but possibly any hollow organ that has been "unblocked". This term is common in vascular surgery, cardiac surgery, interventional radiology, or interventional cardiology following angioplasty, all branches of medicine that frequently treat stenotic lesions.
There are probably several mechanisms that lead to restenosis. An important one is the inflammatory response, which induces tissue proliferation - (to cause to grow or increase rapidly) around an angioplasty site.
Cardiologists have tried a number of approaches to decrease the risk of restenosis. Stenting is becoming more commonplace; replacing balloon angioplasty. During the stenting procedure, a metal mesh (stent) is deployed against the wall of the artery revascularizing the artery. Other approaches include local radiotherapy and the use of immunosuppressive drugs, coated onto the stenting mesh. Analogues of rapamycin, such as tacrolimus (FK-506), sirolimus and more so everolimus, normally used
as immunosuppressants but recently discovered to also inhibit the proliferation of vascular smooth muscle cells, have appeared to be quite effective in preventing restenosis in clinical trials. Antisense knockdown of c-myc, a protein critical for progression of cell replication, is another approach to inhibit cell proliferation in the artery wall and has been through preliminary clinical trials using Morpholino oligosis – (a kind of molecule used to modify gene expression. Morpholino oligonucleotides (oligos) are an antisense technology used to block access of other molecules to specific sequences within nucleic acid).
Rheumatic heart disease .
Rheumatism or Rheumatic disorder is a non-specific term for medical problems affecting the heart, bones, joints, kidney, skin and lung. The study of, and therapeutic interventions in, such disorders is called rheumatology.
The term "rheumatism" is still used in colloquial speech and historical contexts, but is no longer frequently used in medical or technical literature; it would be fair to say that there is no longer any recognized disorder simply called "rheumatism". The traditional term covers such a range of different problems that to ascribe symptoms to "rheumatism" is not to say very much. Nevertheless, sources dealing with rheumatism tend to focus on arthritis.
Sellick Manoeuver (Cricoid Pressure).
The Sellick (or Sellick's) manoeuver is a method of preventing regurgitation of an anaesthetised patient during endotracheal intubation by applying pressure to the cricoid cartilage -(from the Greek krikoeides meaning "ring-shaped"), is the only complete ring of cartilage around the trachea). The Sellick manoeuver is performed by applying gentle pressure to the anterior neck at the level of the cricoid cartilage. The Manoeuver is used to help align the airway during endotracheal intubation. The reason for performing the Sellick manoeuver is to provide a means to prevent gastric insufflation–(to blow or breathe something in) and vomiting during ventilations in an unprotected airway. This method is employed early until a properly placed endotracheal tube has been inserted. Aspiration pneumonitis-(is bronchopneumonia that develops due to the entrance of foreign material that enter the bronchial tree) has a high mortality rate and proper use of this method can minimize its occurrence.
Sedation is a medical procedure involving the administration of sedative drugs, generally to facilitate a medical procedure with local anaesthesia-( is any technique to render part of the body insensitive to pain without affecting consciousness).
Sepsis is a serious medical condition characterized by a whole-body inflammatory state caused by infection. Traditionally the term sepsis has been used interchangeably with septicaemia ("blood poisoning") However, these terms are no longer considered synonymous; septicaemia is considered a subset of sepsis.
Septicemia: Systemic (bodywide) illness with toxicity due to invasion of the bloodstream by virulent bacteria coming from a local seat of infection. The symptoms of chills, fever and exhaustion are caused by the bacteria and substances they produce. The disorder is treated with massive doses of antibiotics. Septicemia - (also known as blood poisoning).
Shock is a serious medical condition where the tissue perfusion is insufficient to meet demand for oxygen and nutrients. This hypo-perfusional state is a life-threatening medical emergency and one of the leading causes of death for critically ill people. This primary cause may lead to many other medical emergencies, such as hypoxia or cardiac arrest .
Sick sinus syndrome.
Sick sinus syndrome: Symptoms of dizziness, confusion, fainting, and heart failure due to a problem with the sinus node of the heart, which acts as the body's natural pacemaker. If the sinus node is not functioning normally, it is reflected in an abnormally slow heart rate (bradycardia). This can cause poor pumping by the heart, which can impair the circulation. Diagnosis is usually by electrocardiogram (ECG). Treatment includes medications, such as the class of drugs called calcium antagonists.
The normal regular rhythm of the heart set by the natural pacemaker of the heart called the sinoatrial (or sinus) node. It is located in the wall of the right atrium ( the right upper chamber of the heart ). Normal cardiac impulses start there and are transmitted to the atria and down the ventricles (the lower chambers of the heart).Normal rate is between 60 and 100 beats per minute ( B.P.M ).
• normal ECG tracing.
• P waves are present
• p wave configuration is constant
• P wave has a normal axis
• each P wave is followed by a QRS complex at an interval between 120 and 200 ms
• QRS complexes are of normal width
• the intervals between QRS complexes are equal
• the heart rate is between 60 and 100 beats per minute
• sinus bradycardia is present if the heart rate is lower than 60 beats per minute
• sinus tachycardia is present if the heart rate is higher than 100 beats per minute
Skeletal muscle is a type of striated muscle-(see smooth muscle), usually attached to the skeleton. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction.
They generally contract voluntarily (via somatic nerve stimulation), although they can contract involuntarily through reflexes.
Smooth muscle is a type of non-striated muscle, found within the "walls" of hollow organs and elsewhere like the bladder and abdominal cavity, the uterus, male and female reproductive tracts, the gastrointestinal tract, the respiratory tract, the vasculature, the skin and the ciliary muscle and iris of the eye, the glomeruli of the kidneys contain a smooth muscle. Smooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure and function.
Striated muscle can refer to:
• Skeletal muscle
• Cardiac muscle
In practice, the term "striated muscle" is sometimes used to refer exclusively to skeletal muscle when distinguishing it from smooth muscle. However, different medical dictionaries report different usages of the terms. Cardiac muscle is a different type of muscle, but has almost the same structure as skeletal muscle.
Sodium (see electrolytes).
Sodium is a chemical element which has the symbol Na (Latin: natrium), atomic number 11.Sodium is a soft, silvery white, highly reactive element. It has only one stable isotope. Sodium is present in great
quantities in the earth's oceans as sodium chloride. It is also a component of many minerals, and it is an essential element for animal life. As such, it is classified as a “dietary inorganic macro-mineral.”
Sodium chloride, also known as common salt, table salt, is a chemical compound with the formula NaCl.
Sodium channels (also known as "voltage-gated sodium channels") are integral membrane proteins that conduct sodium ions (Na+) through a cell's plasma membrane. Many of the ionotropic receptors are also able to conduct sodium ions and are discussed elsewhere. In excitable cells such as neurons and myocytes, sodium channels are responsible for the rising phase of action potentials.
A spasm is a sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ, or a similarly sudden contraction of an orifice. It is sometimes accompanied by a sudden burst of pain, but is usually harmless and ceases after a few minutes. Spasmodic muscle contraction may also be due to a large number of medical conditions.
Spinal anaesthesia is a form of local, or more specifically regional, anaesthesia involving injection of a local anaesthetic into the cerebrospinal fluid (CSF), generally through a long fine needle.
There are hyperbaric - (of an anesthetic) having a specific gravity greater than that of cerebrospinal fluid), isobaric, hypobaric solutions of anaesthetics to choose for the spinal anaesthesia. Usually, the hyperbaric is chosen. Bupivacaine is the local anesthetic most commonly used, although lignocaine, ropivacaine, levobupivicaine and cinchocaine are also available. Regardless of the anaesthetic agent used, the desired effect is to block the transmission of nerve signals to and from the affected area. Sensory signals from the site are blocked, thereby eliminating pain, and motor signals to the area eliminate movement. In effect, the result is total numbness of the area and paralysis. This allows medical procedures to be performed with little or no sensation whatsoever to the person undergoing the procedure, and provides a still patient or area for the surgeon to work on. Typically some sedation is provided to help the patient relax and pass the time during the procedure, but with a successful spinal anesthetic the surgery could be performed with the patient wide awake. Spinal anesthetics are limited to procedures involving most structures below the upper abdomen, as to administer a spinal anesthetic higher may affect the ability to breathe by paralysing the intercostal respiratory muscles, or even the diaphragm in extreme cases (high spinal), as well as the body's ability to control the heart rate.
A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure. It is also sometimes called a "stricture" (as in urethral stricture). Stenoses of the vascular type are often associated with a noise (bruit -is the term for the unusual sound that blood makes when it rushes past an obstruction in an artery) resulting from turbulent flow over the narrowed blood vessel. This bruit can be made audible by a stethoscope. Other, more reliable methods of diagnosing a stenosis are imaging methods including ultrasound, Magnetic Resonance Imaging/Magnetic Resonance Angiography, Computed Tomography/CT-Angiography which display anatomic imaging (i.e. the visible narrowing of a vessel) and/or flow phenomena (signs of the movement of the bodily fluid through the bodily structure).
In medicine, a stent is either an expandable wire form or perforated tube (conventionally perforated by means of laser cutting) that is inserted into a natural conduit of the body to prevent or counteract a disease-induced localized flow constriction. The main purpose of a stent is to counteract significant decreases in vessel or duct diameter by acutely propping open the conduit by a mechanical scaffold or stent. Stents are often used to alleviate diminished blood flow to organs and extremities beyond an obstruction in order to maintain an adequate delivery of oxygenated blood. Although the most common use of stents is in coronary arteries, they are widely used in other natural body conduits, such as central and peripheral arteries and veins, bile ducts, oesophagus, colon, trachea or large bronchi, ureters, and urethra.
Median sternotomy is a type of surgical procedure in which a vertical inline incision is made along the sternum, after which the sternum itself is divided, or "cracked". This procedure provides access to the heart and lungs for surgical procedures such as heart transplant, corrective surgery for congenital heart defects (CHD's), or coronary artery bypass surgery.
Median sternotomy is often mistakenly referred to as open heart surgery; however, open heart involves incision of the pericardium, and many median sternotomy procedures do not require this. Open heart usually involves the use of a cardiopulmonary bypass, also known as a heart-lung machine.
The sternum (from Greek στέρνον, sternon, "chest") or breastbone is a long, flat bone located in the center of the thorax (chest). It connects to the rib bones via cartilage, forming the rib cage with them, and thus helps to protect the lungs, heart and major blood vessels from physical trauma. The sternum is sometimes cut open (a median sternotomy) to gain access to the thoracic contents when performing cardiothoracic surgery.
1. Any of a large class of organic compounds having as a basis 17 carbon atoms arranged in four rings fused together. Steroids include many biologically important compounds, including cholesterol and other sterols, the sex hormones (such as testosterone and oestrogen), bile acids, adrenal hormones, plant alkaloids, and certain forms of vitamins.
2. Any of various hormones having the structure of a steroid that are made synthetically, especially for use in medicine.
3. An anabolic steroid, a class of steroid hormones related to the hormone testosterone. ( anabolic comes from the Greek: anabole, "to build up").
Stokes-Adams syndrome: recurrent sudden attacks of unconsciousness caused by impaired conduction of the impulse that regulates the heartbeat ( syn: heart block, Stokes-Adams syndrome, atrio-ventricular block ).
Stroke (or cerebrovascular accident or CVA) is the clinical designation for a rapidly developing loss of brain function due to an interruption in the blood supply to all or part of the brain. This phenomenon can be caused by thrombosis, embolism, or haemorrhage. In medicine the process of being struck down by a stroke, fit or feint is sometimes called an ictus, from the Latin icere (“to strike”), especially prior to the definitive diagnosis being made.
Stroke output (see Cardiac Output).
Stroke volume (see Cardiac Output).
Stroke volume is the amount of blood pumped by the left ventricle of the heart in one contraction. The stroke volume is not all of the blood contained in the left ventricle. The heart does not pump all the blood out of the ventricle. Normally, only about two-thirds of the blood in the ventricle is put out with each beat. What blood is actually pumped from the left ventricle is the stroke volume and it, together with the heart rate, determines the cardiac output.
The ST segment connects the QRS complex and the T wave and has a duration of 0.08 to 0.12 sec (80 to 120 ms). It starts at the J point (junction between the QRS complex and ST segment) and ends at the beginning of the T wave. However, since it is usually difficult to determine exactly where the ST segment ends and the T wave begins, the relationship between the ST segment and T wave should be examined together. The typical ST segment duration is usually around 0.08 sec (80 ms). It should be essentially level with the PR and TP segment.
A 12 lead ECG is used to classify patients into one of three groups:
• The normal ST segment has a slight upward concavity.
• Flat, downsloping, or depressed ST segments may indicate coronary ischemia.
• ST segment elevation may indicate myocardial infarction. An elevation of >1mm and longer than 80 milliseconds following the J-point. This measure has a false positive rate of 15-20% (which is slightly higher in women than men) and a false negative rate of 20-30%.
A normal ECG does not rule out acute myocardial infarction. Sometimes the earliest presentation of acute myocardial infarction is the hyperacute T wave, which is treated the same as ST segment elevation. In practice this is rarely seen, because it only exists for 2-30 minutes after the onset of infarction. Hyperacute T waves need to be distinguished from the peaked T waves associated with hyperkalemia. The current guidelines for the ECG diagnosis of acute myocardial infarction require at least 1 mm (0.1 mV) of ST segment elevation in 2 or more anatomically contiguous leads. This criterion is problematic, however, as acute myocardial infarction is not the most common cause of ST segment elevation in chest pain patients. In addition, over 90% of healthy men have at least 1 mm (0.1 mV) of ST segment elevation in at least one precordial lead. The clinician must therefore be well versed in recognizing the so-called ECG mimics of acute myocardial infarction, which include left ventricular hypertrophy, left bundle branch block, paced rhythm, benign early repolarization, pericarditis, hyperkalemia, and ventricular aneurysm.
Left bundle branch block and pacing can interfere with the electrocardiographic diagnosis of acute myocadial infarction. The GUSTO investigators Sgarbossa et al. developed a set of criteria for identifying acute myocardial infarction in the presence of left bundle branch block and paced rhythm. They include concordant ST segment elevation > 1 mm (0.1 mV), discordant ST segment elevation > 5
ST Segment (cont).
mm (0.5 mV), and concordant ST segment depression in the left precordial leads. The presence of reciprocal changes on the 12 lead ECG may help distinguish true acute myocardial infarction from the mimics of acute myocardial infarction. The contour of the ST segment may also be helpful, with a straight or upwardly convex (non-concave) ST segment favoring the diagnosis of acute myocardial infarction.
The constellation of leads with ST segment elevation enables the clinician to identify what area of the heart is injured, which in turn helps predict the so-called culprit artery.
Wall Affected Leads Showing ST Segment Elevation Leads Showing Reciprocal ST Segment Depression Suspected Culprit Artery
Septal V1, V2 None Left Anterior Descending (LAD)
Anterior V3, V4 None Left Anterior Descending (LAD)
Anteroseptal V1, V2, V3, V4 None Left Anterior Descending (LAD)
Anterolateral V3, V4, V5, V6, I, aVL II, III, aVF Left Anterior Descending (LAD), Circumflex (LCX), or Obtuse Marginal
Extensive anterior (Sometimes called Anteroseptal with Lateral extension) V1,V2,V3, V4, V5, V6, I, aVL II, III, aVF Left main coronary artery (LCA)
II, III, aVF I, aVL Right Coronary Artery (RCA) or Circumflex (LCX)
Lateral I, aVL, V5, V6 II, III, aVF Circumflex (LCX) or Obtuse Marginal
Posterior (Usually associated with Inferior or Lateral but can be isolated) V7, V8, V9 V1,V2,V3, V4 Posterior Descending (PDA) (branch of the RCA or Circumflex (LCX))
Right ventricular (Usually associated with Inferior) II, III, aVF, V1, V4R I, aVL Right Coronary Artery (RCA)
As the myocardial infarction evolves, there may be loss of R wave height and development of pathological Q waves. T wave inversion may persist for months or even permanently following acute myocardial infarction. Typically, however, the T wave recovers, leaving a pathological Q wave as the only remaining evidence that an acute myocardial infarction has occurred.
The sub-cutis is the layer of tissue directly underlying the cutis-(the outermost layers of skin ). It is mainly composed of adipose- (fat) tissue. Its physiological function includes insulation and storage of nutrients. Subcutaneous injections are given by injecting a fluid into the sub-cutis. It is relatively painless and an effective way to administer particular types of medication.
A rapid rhythym of the heart in which the origin of the electrical signal is either the atria or AV node. These rhythms require the atria or AV node for initiation or maintanence. This is in contrast to ventricular tachycardias( VTs ),which are tachycardias that are not dependant on the atria or AV node.
• P waves are present, but they may be hidden within the T wave
• each P wave is followed by a QRS complex at an interval between 0,12 and 0,2 s
• the PR interval can be shorter at a higher heart rate
• the intervals between QRS complexes are equal
• heart rate is between 100 and 260 beats per minute
Supraventricular - means 'coming from above the ventricles'.
Swan Ganz catheter.
In medicine pulmonary artery catheterisation is the insertion of a catheter into a pulmonary artery. Its purpose is diagnostic; it is used to detect heart failure or sepsis, monitor therapy, and evaluate the effects of drugs. The pulmonary artery catheter allows direct, simultaneous measurement of pressures in the right atrium, right ventricle, pulmonary artery, and the filling pressure ("wedge" pressure) of the left atrium. The pulmonary artery catheter is frequently referred to as a Swan-Ganz catheter, in honour of its inventors Jeremy Swan and William Ganz, from Cedars-Sinai Medical Center. The idea for this catheter (as later revealed by Dr. Swan) came about from the observation of sailboats on the water.
• Management of complicated myocardial infarction
o Hypovolaemia vs cardiogenic shock
o Ventricular septal rupture (VSR) vs acute mitral regurgitation
o Severe left ventricular failure
o Right ventricular infarction
Swan Ganz catheter (cont).
• Unstable angina
• Refractory ventricular tachycardia
• Assessment of respiratory distress
o Cardiogenic vs non-cardiogenic pulmonary edema
o Primary vs secondary pulmonary hypertension
• Assessment of type of shock
• Assessment of therapy
o Afterload reduction
o Beta blockers
o Intra-aortic balloon counterpulsation
• Assessment of fluid requirement in critically ill patients
o Acute renal failure
• Management of postoperative open heart surgical patients
• Assessment of valvular heart disease
• Assessment of cardiac tamponade/constriction
The catheter is introduced through a large vein—often the internal jugular, subclavian, or femoral veins, through the right atrium of the heart, the right ventricle, and subsequently into the pulmonary artery.
The standard pulmonary artery catheter is equipped with an inflatable balloon at the tip, which facilitates its placement into the pulmonary artery through the flow of blood. The balloon, when inflated, causes the catheter to "wedge" in a small pulmonary blood vessel. So wedged, the catheter can provide a measurement of the pressure in the left atrium of the heart.
The procedure is not without risk, and complications can be life threatening. It can lead to arrhythmias, rupture of the pulmonary artery, thrombosis, infection, pneumothorax and bleeding.
Sympathetic nervous system.
One of two divisions of the autonomic( self governing ) nervous system, ( sympathetic and parasympathetic). It supplies involuntary muscle and glands; it stimulates the ductless glands and the circulatory and respiratory systems, but inhibits the digestive systems.
Sympathomimetic drugs are substances that mimic the effects of the hormone adrenaline and the hormone/neurotransmitter noradrenaline. They all raise blood pressure and are all weak bases.
In medicine, a disease is symptomatic when it is at a stage when the patient is experiencing symptoms. It is generally used in counter-distinction of asymptomatic (when the disease is in-
apparent). Symptomatic treatment is the practice of treating a patient's symptoms, rather than the disease or injury itself.
Synapse / Synaptic.
Chemical synapses are specialized junctions through which the cells of the nervous system signal to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow the neurons of the central nervous system to form interconnected neural circuits.
Synthetic / Synthesis.
Artificial, synthesis, the building up of a more complex structure from simple components.
Systemic means "affecting the entire body," rather than a single organ or body part.
Systole is the contraction of heart chambers, driving blood out of the chambers. The chamber most often discussed is the left ventricle. However, all four chambers of the heart undergo systole and diastole in a timed fashion so that blood is propelled forward through the cardiovascular system.
Systolic anterior motion (SAM)
Systolic anterior motion (SAM) is a postoperative complication experienced by patients undergoing mitral valve repair. The incidence of SAM after mitral valve repair ranges from 5 to 10%. Early recognition of the signs and symptoms of SAM is imperative to the management of these patients. Systolic anterior motion of the mitral valve (SAM) occurs when the anterior leaflet of the mitral valve is "pulled" into the outflow tract of the left ventricle during the systolic phase of the cardiac cycle. This causes the mitral valve to leak back into the left atrium.
Tachycardia means a fast heart rate.
Tamponade is a condition of blood flow stoppage either by insertion of a tampon (a wadded cotton plug) into a blood vessel or by a constriction of the vessel by an outside force.
Cardiac tamponade, also known as pericardial tamponade, is a medical emergency condition in which fluid accumulates in the pericardium (the sac in which the heart is enclosed). The elevated pericardial pressure puts significant pressure on the heart, causing a decrease in diastolic filling of the ventricles, and hence in stroke volume. The end result is ineffective pumping of blood, shock and often death.
Thromboelastograph( T.E.G ).
Apparatus for registering elastic variations of a thrombus during the process of coagulation. The thromboelastograph consists of two concentric cylinders with a space between them. The outer cylinder (cuvette) of the thromboelastograph oscillates at a fixed frequency. The internal cylinder (pin) of the thromboelastograph is free to move. As a blood sample placed between the cylinders clots, it forms a mechanical bond between the inner and outer cylinders of the thromboelastograph such that the oscillatory motion of the outer cylinder is imparted to the inner cylinder. A plot of the movement of the inner cylinder is known as a thromboelastogram. A stronger clot results in a tighter mechanical coupling between the two cylinders and a larger transmitted oscillation of the inner cylinder. Variation over time of the clot strength results in different thromboelastogram profiles that are useful for diagnosis. Feature extraction is applied to the resulting thromboelastogram to arrive at specific parameters such as R, K, Ang, MA and LY30. The thromboelastogram is used to diagnose different conditions such as fibrinolysis, thrombocytopaenia ( reduced platelet (thrombocyte) count) , and factor deficiency.
Thiazide diuretics are a common treatment for high blood pressure. They are also used to clear fluid from the body in conditions where your body accumulates too much fluid such as
Thoracic surgery is the field of medicine involved in the surgical treatment of diseases affecting organs inside the thorax (the chest) excluding the heart. Generally treatment of conditions of the lungs, chest wall, oesophagus and diaphragm. Cardiac surgery and thoracic surgery are separate surgical specialties, but are frequently grouped together as cardiothoracic surgery. Cardiac surgery generally refers surgery of the heart and great vessels, and thoracic surgery generally refers to surgery of the chest other than the heart. A cardiothoracic surgeon will perform surgery within the realm of both cardiac and thoracic surgery.
Thoracotomy is an incision into the chest. It is performed by a surgeon, and, rarely, by emergency physicians and paramedics, to gain access to the thoracic organs, most commonly the heart, the lungs, the oesophagus or thoracic aorta, or for access to the anterior spine such as is necessary for access to tumors in the spine. Thoracotomy is a major surgical manoeuver—the first step in cardiothoracic surgery, which involves major procedures such as coronary artery bypass surgery and lobectomy or pneumonectomy for lung cancer—and as such requires general anesthesia with endo-tracheal tube insertion and mechanical ventilation.
There probably are many different approaches to thoracotomy. The most common modalities of thoracotomy follow.
Median sternotomy provides wide access to the mediastinum and is the incision of choice for most open-heart surgery and access to the anterior mediastinum.
Postero-lateral thoracotomy is a very common approach for operations on the lung or posterior mediastinum, including the oesophagus. When performed over the 5th intercostal space, it allows optimal access to the pulmonary hilum-(is a depression or pit at the part of an organ where structures such as blood vessels and nerves enter ) (pulmonary artery and pulmonary vein) and therefore is considered the approach of choice for pulmonary resection (pneumonectomy and lobectomy).
Antero-lateral thoracotomy is performed upon the anterior chest wall; left antero-lateral thoracotomy is the incision of choice for open chest massage, a critical manoeuver in the management of traumatic cardiac arrest. Antero-lateral thoracotomy, like most surgical incisions, requires the use of tissue retractors—in this case, a "rib spreader" such as the Tuffier retractor.
Bilateral antero-lateral thoracotomy combined with transverse sternotomy results in the "clamshell" incision, the largest incision commonly used in thoracic surgery.
Upon completion of the surgical procedure, the chest is closed. One or more chest tubes—with one end inside the opened pleural cavity and the other submerged under saline solution inside a sealed container, forming an airtight drainage system—are necessary to remove air and fluid from the pleural cavity, preventing the development of pneumothorax or haemothorax.
In addition to pneumothorax, complications from thoracotomy include air leaks, infection, bleeding and respiratory failure. Postoperative pain is universal and intense, generally requiring opioids, and does interfere with the recovery of respiratory function.
Video-assisted thoracic surgery (VATS) is a less invasive alternative to thoracotomy in selected cases, much like laparoscopic surgery. Like laparoscopic surgery, its applications are rapidly expanding. Robotic surgery is a new but rarely used innovation with questionable advantages.
Thorax / Thoracic.
The thorax is the region of the body formed by the sternum- (or breastbone is a long, flat bone located in the center of the thorax (chest), the thoracic vertebrae and the ribs. It extends from the neck to the diaphragm, not including the upper limbs. The heart and the lungs reside in the thoracic cavity, as well as many blood vessels. The inner organs are protected by the rib cage and the sternum.
Thrombocytes are also known as platelets. They are metabolically active cell fragments that are important in haemostasis.(see platelets).
Thrombolysis is the breakdown (lysis) of blood clots by pharmacological means. It is colloquially referred to as clot busting for this reason. It works by stimulating fibrinolysis by plasmin through infusion of analogs of tissue plasminogen activator, the protein that normally activates plasmin.
Thrombolysis requires the use of thrombolytic drugs, which are either derived from Streptomyces spp. or (more recently) the effect of recombinant technology, where human activators of plasminogen (e.g. tissue plasminogen activator, tPA) are manufactured by bacteria.
Some commonly used thrombolytics are
• alteplase (recombinant tissue plasminogen activator or rtPA).
Formation of blood clots lies at the basis of a number of serious diseases. By breaking down the clot, the disease process can be arrested, or the complications reduced. While other anticoagulants (such as heparin) decrease the "growth" of a clot, thrombolytic agents actively reduce the size of the clot.
All thrombolytic agents work by activating the enzyme plasminogen, which clears the cross-linked fibrin mesh (the backbone of a clot). This makes the clot soluble and subject to further proteolysis by other enzymes, and restores blood flow over occluded blood vessels.
Diseases where thrombolysis is used:
• Myocardial infarction
• Stroke (ischemic stroke)
• Massive pulmonary embolism
• Acute limb ischaemia
Apart from streptokinase, all thrombolytic drugs are administered together with heparin (unfractionated or low molecular weight heparin), usually for 24-48 hours.
Thrombolysis is usually intravenous. It may also be used during an angiogram (intra-arterial thrombolysis), e.g. when patients present with stroke beyond three hours.
Thrombophlebitis is phlebitis (vein inflammation) related to a blood clot or thrombus. When it occurs repeatedly in different locations, it is known as "Thrombophlebitis migrans" or "migrating thrombophlebitis".
Causes, incidence, and risk factors:
Thrombophlebitis ( another medical term is "White Leg" ) is related to a blood clot (thrombus) in the vein. Risk factors include prolonged sitting and disorders related to blood clotting. Specific disorders associated with thrombophlebitis include superficial thrombophlebitis (affects veins near the skin surface) and deep venous thrombosis (affects deeper, larger veins).
The following symptoms are often (but not always) associated with thrombophlebitis:
• pain in the part of the body affected.
• skin redness or inflammation (not always present).
• swelling (oedema) of the extremities (ankle and foot).
Thrombosis is the formation of a clot or thrombus inside a blood vessel, obstructing the flow of blood through the circulatory system. Thrombo-embolism is a general term describing both thrombosis and its main complication which is embolisation.
The average pair of human lungs can hold about 6 liters of air, but only a small amount of this capacity is used during normal breathing. Lung volumes refer to physical differences in volume, while lung capacities represent different combinations of lung volumes, usually in relation to respiration and exhalation. Breathing mechanism in mammals is called "tidal breathing". Tidal breathing means that air goes into the lungs the same way that it comes out. The tidal volume, vital capacity, inspiratory capacity and expiratory reserve volume can be measured directly with a spirometer.
Biological tissue is a collection of interconnected cells that perform a similar function within an organism. The study of tissue is known as histology, or, in connection with disease, histopathology. There are four basic types of tissue in the human body. These compose all the organs, structures and other contents.
• Epithelium - Tissues composed of layers of cells that cover organ surfaces such as surface of the skin and inner lining of digestive tract: the tissues that serve for protection, secretion, and absorption.
• Connective tissue - As the name suggests, connective tissue holds everything together. Connective tissue is characterized by the separation of the cells by an inorganic material, which is called extra-cellular matrix. Bone and blood are connective tissues.
• Muscle tissue - Muscle cells contain contractile filaments that move past each other and change the size of the cell. Muscle tissue also is separated into three distinct categories: visceral or smooth muscle, which is found in the inner linings of organs; skeletal muscle, which is found attached to bone in order for mobility to take place; and cardiac muscle which is found in the heart.
• Nervous tissue - Cells forming the brain, spinal cord and peripheral nervous system.
Torsades de points
Torsades de pointes or torsades is a French term that literally means "twisting of the points". It refers to a specific variety of ventricular tachycardia and its name is derived from a manoeuver in ballet. On the electrocardiogram, torsades is irregular, polymorphic, and often exhibits a "streamer" effect as the QRS complex transitions from positive to negative, and back again. Clinically speaking, the difference between polymorphic (multiple states) ventricular tachycardia and torsades de pointes is the presence of a prolonged QT interval in the underlying rhythm of the latter.
Ventricular tachycardia "Torsade de pointes"
• ventricular tachycardia with the QRS complexes that change direction in the ECG
• QRS complexes are bizarre and of different shapes
• the rate is usually 100 do 180 beats per minute, occasionally up to 300 beats per minute
• this form of ventricular tachycardia degenerates relatively often into ventricular fibrillation
Toxicity is a measure of the degree to which something is toxic or poisonous. The study of poisons is known as toxicology. Toxicity can refer to the effect on a whole organism, such as a human or a bacterium or a plant, or to a substructure, such as a cell (cytotoxicity) or an organ (organotoxicity such as the liver (hepatotoxicity). By extension, the word may be metaphorically used to describe toxic effects on larger and more complex groups, such as the family unit or "society at large".
The trachea, or windpipe, is a tube that has an inner diameter of about 20-25 mm and a length of about 10-16cm. It extends from the larynx to the primary (main) bronchi in mammals, allowing the passage of air to the lungs. It is lined with pseudo-stratified ciliated columnar epithelium cells with mucosae goblet cells which produce mucus. This lines the cells of the trachea to trap inhaled foreign particles which the cilia then waft upwards towards the larynx and then the pharynx where it can then be swallowed into the stomach. In humans there are about 15 – 20 incomplete C-shaped cartilaginous rings which reinforces the anterior and lateral sides of the trachea to protect and maintain the airway open. There is a piece of smooth muscle connecting the ends off the incomplete cartilaginous rings called the trachealis muscle. This contracts reducing the size of the lumen of the trachea to increase the air flow rate during coughing. The oesophagus lies posteriorly to the trachea. The cartilaginous rings are incomplete because this allows the trachea to collapse slightly to allow food to pass down the oesophagus. The epiglottis is the flap that closes the trachea during swallowing to prevent swallowed matter from entering the trachea.
A tracheotomy is a procedure performed by paramedics, emergency physicians and surgeons in order to secure an airway. A tracheotomy or tracheostomy is a surgical procedure performed on the neck to open a direct airway through an incision in the trachea (the windpipe). (Technically, the former term, with the Greek root tom- meaning "to cut," refers to the procedure of cutting into the trachea, whereas the latter term, with the root stom- meaning "mouth," refers to the procedure of making a semi-permanent or permanent opening. Tracheostomy can also refer to the result of the procedure, i.e. the opening itself.).
The conditions in which a tracheotomy may be used are:
• Acute setting - maxillofacial injuries, large tumors of the head and neck, congenital tumors, e.g. branchial cyst, acute inflammation of head and neck, and
• Chronic / elective setting - when there is need for long term mechanical ventilation and tracheal toilet, e.g. comatose patients, surgery to the head and neck,and long term I.T.U patients.
In emergency settings, in the context of failed endotracheal intubation or where intubation is contraindicated, cricothyroidotomy-( is an emergency incision through the skin and cricothyroid membrane to secure a patient's airway during certain emergency situations, an incision on the skin of the neck just below the "Adam's apple",) or mini-tracheostomy may be performed in preference to a tracheostomy.
For a short time only.
Trans-Oesophagael Echocardiogram (T.O.E):
A specialized probe containing an ultrasound transducer at its tip is passed into the patient's oesophagus. This allows image and Doppler evaluation which can be recorded. This is known as a trans-oesophageal echocardiogram, or ( TOE ). The heart rests directly upon the oesophagus leaving only millimeters in distance that the ultrasound beam has to travel. This reduces the attenuation of the ultrasound signal engendering a stronger return signal, ultimately enhancing image and Doppler quality. Comparatively, trans-thoracic ( TTE ), ultrasound must first traverse skin, fat, ribs and lungs before reflecting off the heart and back to the probe before an image can be created. All these structures, and the distance the beam must travel, attenuate the ultrasound signal, degrading image and Doppler quality. In adults, several structures can be evaluated and imaged better with the TOE, including the aorta, pulmonary artery, valves of the heart, both atria, atrial septum, left atrial appendage, and coronary arteries. While TTE can be performed quickly, easily and without pain for the patient, TOE requires a fasting patient, a team of medical personel, takes longer to perform, is uncomfortable for the patient and has significant risks associated with the procedure (oesophageal perforation--1 in 10,000, and adverse reactions to the medication).
Physical trauma refers to a physical injury. A trauma patient is someone who has suffered serious and life-threatening physical injury potentially resulting in secondary complications such as shock, respiratory failure and death.
Trauma (plurals: traumata, traumas) can represent:
• Physical trauma, an often serious and body altering physical injury, such as the removal of a limb
• Psychological trauma, an emotional or psychological injury, usually resulting from an extremely stressful or life-threatening situation
• Blunt force trauma, a type of physical trauma caused by impact or other force applied from or with a blunt object
• Penetrating trauma, a type of physical trauma in which the skin or tissues are pierced by an object .
Tricuspid Annuoplasty /repair ( T.A ).
Usually, mild tricuspid regurgitation requires little or no treatment. However, the underlying disorder, such as emphysema, pulmonary hypertension, pulmonic stenosis, or abnormalities of the left side of the heart, is likely to require treatment. Treatment of atrial fibrillation and heart failure is also necessary, but surgery to repair the tricuspid valve is rarely done unless surgery on another heart valve (for example, mitral valve replacement) is also needed. When valve disease is severe, it may be necessary to repair or replace the diseased valve. Tricuspid valve repair using an annuloplasty ring-(annul-having the form of a ring) (plasty-a surgical procedure for the repair, restoration, or replacement (as by a prosthesis), a ring of tough fibrous tissue which is attached to and supports the leaflets of the valve is the preferred surgical approach for tricuspid regurgitation and may be performed for primary tricuspid disease or for combined cases with other valve surgery (mitral, aortic). Tricuspid regurgitation (tricuspid incompetence, tricuspid insufficiency) is leakage of blood backward through the tricuspid valve each time the right ventricle contracts. As the right ventricle contracts to pump blood forward to the lungs, some blood leaks backward into the right atrium, increasing the volume of blood there and resulting in less blood being pumped through the heart and to the body. As a result, the right atrium enlarges, and blood pressure increases in the right atrium and the large veins that enter it from the body. The liver may swell because of this increased pressure. Enlargement of the right atrium also can result in atrial fibrillation, a rapid, irregular heartbeat. Eventually, heart failure develops.