A thru C | D thru O | P thru Z (This page below)

Pacemaker - The "natural" pacemaker of the heart is called the sinus node. It's a small group of specialized cells in the top of the heart's right chamber (atrium). It produces the electrical impulses that travel down to the heart's lower chambers (ventricles), causing the heart to contract. An "artificial pacemaker" is an electrical device that can substitute for a defective natural pacemaker or conduction pathway. An artificial pacemaker regulates the speed and rhythm of the heartbeat. Usually these devices are used for hearts that beat too slowly. Pacemakers run on batteries and usually last many years.

Palpitations - The sensation of the heart beating rapidly or irregularly.

Paramedical - Pertaining or closely related to the art or practice of medicine. This term is often applied to personnel whose work supports, or is closely related to, that of practicing physicians.

Patent Ductus Arteriosus (PDA) - A congenital heart defect that allows blood to mix between the pulmonary artery and the aorta. Before birth an open passageway (the ductus arteriosus) exists between these two blood vessels. Normally this closes within a few hours of birth. When this doesn't happen, some blood that should flow through the aorta and on to nourish the body returns to the lungs. A ductus that doesn't close is quite common in premature infants but rather rare in full-term babies. If the ductus arteriosus is large, a child may tire quickly, grow slowly, catch pneumonia easily and breathe rapidly. In some children symptoms may not occur until after the first weeks or months of life. If the ductus arteriosus is small, the child seems well. If surgery is needed, the surgeon can close the ductus arteriosus by tying it, without opening the heart. If there's no other defect, this restores the circulation to normal.

Percutaneous Transluminal Coronary Angioplasty (PTCA) - (See Angioplasty)

Perfusion - Blood flow.

Pericarditis - A disorder caused by inflammation of the pericardium, which is the sac-like covering of the heart. It is usually a complication of a viral, bacterial or fungal infection. It can also result from a heart attack, cancer, radiation treatment, injury or surgery. It most often affects men ages 20-50, but can also occur in children.

Pericardium - The outer fibrous "sac" that surrounds the heart.

Peripheral Artery Disease (PAD) - A type of peripheral vascular disease that affects blood circulation, mainly in arteries leading to the legs and feet. It's caused by atherosclerosis. Symptoms include pain in the legs or buttocks when exercising that goes away when the activity is stopped, though not everyone has symptoms. Smokers are at a much higher risk for PAD. It can be diagnosed with a quick, painless test called an Ankle-Brachial Index (ABI) Test. Since it often goes undiagnosed, it's important to ask a healthcare professional to administer the test if you have symptoms or smoke.

Peripheral Vascular Disease - Diseases of blood vessels outside the heart and brain or diseases of the lymph vessels. Often it is a narrowing of vessels carrying blood to leg and arm muscles. Peripheral artery disease (PAD) is a common form of peripheral vascular disease.

Phlebotomy - Removal of blood from the vein. This term applies to routine laboratory blood tests, but in patients with high blood counts (See Polycythemia), a larger amount of blood is removed and replaced with intravenous fluid to lower the blood count.

Phospholipid - A type of fat (lipid) that contains phosphorous. It splits into fatty acids, glycerin and a nitrogen compound when water is added.

Plaque - Also called atheroma, this is a cholesterol-laden buildup in the interior wall of blood vessels. After years it may become calcified and hard. It may also rupture. If this happens, a blood clot may form on the plaque and block blood flow, potentially causing a heart attack or stroke. The building up of plaque and hardening of the arteries is known as atherosclerosis.

Plasma Lipid - The lipid (fatty particles) carried in blood.

Platelets - An element in blood that aids in blood clotting.

Polycythemia - An elevated number of red blood cells, also referred to as a "high hematocrit" or "thick blood." Polycythemia is often seen in patients with lower-than-normal levels of oxygen in the blood.

Polyunsaturated Fats - A type of fat found mainly in vegetable oils such as corn, safflower, sunflower and soybean oils. They're usually liquid at room temperature. They may help lower blood cholesterol level when used in place of saturated fats.

Potassium (K+) - One of the electrolyte substances found naturally in the body that, together with sodium and calcium, regulates the body's water balance, maintains normal heart rhythm and is responsible for nerve impulse conduction and muscle contraction. A proper balance of potassium, sodium, calcium and magnesium is essential for normal excitability of muscle tissue, especially cardiac muscle, and plays a role in nerve conduction. Potassium levels are mainly controlled by the steroid hormone aldosterone, which causes the body to rid itself of excess potassium. Small changes in the potassium concentration outside cells can have substantial effects on the activity of nerves and muscles. This is particularly true of heart muscle. Low levels of potassium cause increased activity, which can lead to an irregular heartbeat (arrhythmia). High levels cause decreased activity. Either situation can lead to cardiac arrest in some circumstances.

Premature Atrial Contraction (PAC) - An early beat of the heart's upper chamber (atrium) that may feel like the heart "skipped" a beat. (See also Palpitations.)

Premature Ventricular Contraction (PVC) - An early beat of the heart's lower chamber (ventricle) that may feel like the heart "skipped" a beat. (See also Palpitations.)

Prevalence - The total number of cases of a given disease in a population at a specific time. Prevalence is sometimes expressed as a percentage of population.

Primary Care Doctor - A general internist or family physician who provides patients with routine preventive health care and is their first contact when medical problems arise.

Progestin - Any of a group of steroid hormones that have the effect of the female hormone progesterone. Used in oral contraceptives and hormone replacement therapy. There is also a natural form of progestin.

Prophylaxis - Preventive treatment.

Prostaglandins - One of a number of hormone-like substances that participate in a wide range of body functions such as the contraction and relaxation of smooth muscle, the dilation and constriction of blood vessels, control of blood pressure and modulation of inflammation. Prostaglandins are derived from a chemical called arachidonic acid.

Pulmonary - Pertaining to the lungs.

Pulmonary Artery Catheterization (Right Heart Catheterization) - Used to evaluate primary pulmonary hypertension. In this procedure the doctor places a thin, flexible tube (called a Swan-Ganz catheter) through an artery or vein in the patient's arm, leg or neck and then threads it into the right ventricle and pulmonary artery. This is a common way to measure the pressure in the pulmonary artery and find out what treatment is appropriate for a given patient. It is also used in critically ill patients to provide continuous monitoring of heart function. (Sometimes called Swan-Ganz Catheterization)

Pulmonary Atresia - A congenital heart defect in which no pulmonary valve exists. Blood can't flow from the right ventricle into the pulmonary artery and on to the lungs. This results is a blue discoloration of the skin (cyanosis).

Pulmonary Edema - Fluid buildup (edema) in the lungs usually due to mitral stenosis or left ventricular failure. Symptoms of pulmonary edema include difficulty breathing, coughing up blood, excessive sweating, anxiety and pale skin.

Pulmonary Stenosis (PS) - A congenital heart defect in which the pulmonary or pulmonic valve is defective and doesn't open properly. The pulmonary valve is between the right ventricle and the pulmonary artery. It opens to allow blood to flow from the right ventricle to the lungs. This forces the right ventricle to pump harder than normal to overcome the obstruction. Treatment is needed when the pressure in the right ventricle is higher than normal. In most children the obstruction can be relieved by a procedure called balloon valvuloplasty. Others may need open-heart surge People with pulmonary stenosis, before and after treatment, are at risk for getting an infection of the valve (endocarditis). To help prevent this, they'll need to take antibiotics before certain dental and surgical procedures.

Pulmonary Veins - Four veins that return blood from the lungs to the heart. They empty into the left upper chamber (atrium) of the heart.

Pulmonic (Pulmonary) Valve - The heart valve between the right ventricle and the pulmonary artery. It has three flaps (cusps).

Reentry - A type of abnormal conduction in which electrical impulses get caught in a merry-go-round-like sequence. This is a common cause of tachycardias.

Regurgitation - The leakage that results when a heart valve that doesn't close properly lets blood leak back into the chamber from which it was pumped.

Reperfusion Therapy - One or more techniques to restore blood flow to part of the heart muscle damaged during a heart attack, or part of the brain injured during a stroke. It may include clot-dissolving drugs (thrombolysis), balloon angioplasty or surgery.

Resident - A licensed physician completing training in a primary specialty (e.g., pediatrics, surgery, internal medicine, obstetrics/gynecology, etc.) after medical school.

Restenosis - A renarrowing of an artery after angioplasty, stent or bypass surgery. About one-third of patients who undergo PTCA (percutaneous transluminal coronary angioplasty) have restenosis of the widened segment within about six months of the procedure. Restenosed arteries may have to undergo another angioplasty. Research is now investigating ways to prevent restenosis. Restenosis may also occur in valves after balloon valvuloplasty.

Rheumatic Heart Disease - Damage done to the heart, particularly the heart valves, by one or more attacks of rheumatic fever.

Right Heart Ventriculography - A study of the right chambers (atrium and ventricle) of the heart. This test is used to obtain measurements of pressure, oxygen and cardiac output through a thin flexible tube called a catheter. Occasionally, visualizing the right chambers is also necessary. This is done by injecting contrast media (dye) through the catheter into the heart's right side with a rapid succession of X-rays taken to capture images of blood flow. Right-heart angiography is performed to detect abnormalities in blood flow through the heart's right side.

Right-Sided Heart Failure (Right Ventricular Heart Failure) - Heart failure caused by damage to the heart's right-sided chambers. This usually occurs as a result of left-sided heart failure. When the left ventricle fails, increased fluid pressure is, in effect, transferred back through the lungs, ultimately damaging the heart's right side. When the right side loses pumping power, blood backs up in the body's veins. This usually causes swelling in the legs and ankles.

Risk Factor - An element or condition involving certain hazard or danger. When referring to the heart and blood vessels, a positive risk factor is associated with an increased chance of developing cardiovascular disease including stroke. A negative risk factor is associated with a reduced chance of developing heart and blood vessel disease.

Rubella - Commonly known as German measles.

Saturated Fats - Types of fat found in all foods from animals (i.e., butter, cheese, whole milk, ice cream, cream and fatty meats) and from some plants (i.e., coconut, palm and palm kernel oils). They are the biggest dietary cause of high LDL "bad" cholesterol levels. Limit any foods that are high (for example, over 20 percent) in saturated fat. Limit saturated fat intake to 7-10 percent of total calories (or less) each day. The recommendation for people with coronary heart disease or an LDL cholesterol level of 100 mg/dL or greater is 25-35 percent of calories from fat per day, with less than 7 percent coming from saturated fat.

Septum - The muscular wall dividing the chambers on the heart's left side from the chambers on the right.

Shunt - (1) An abnormal flow pattern of blood through the chambers of the heart or through the large arteries leaving the heart. A "left-to-right" shunt results in extra blood flow entering the lungs, while a "right-to-left" shunt results in decreased blood flow to the lungs, low oxygen levels and cyanosis. (2) A surgically created connection designed to increase the delivery of blood to the lungs. Shunts are also used in bypass surgery and to drain fluids from the body. The most common types of these shunts are named for the physicians who popularized them (Blalock-Taussig, Waterston, Potts, Glenn). A "modified" shunt may involve the use of artificial material, such as Gore-tex®.

Sickle Cell Anemia - A genetic blood disorder that mainly affects African Americans. "Sickled" red blood cells are less able to carry oxygen to the body's tissues and organs. They also tend to stick to blood vessel walls. This can block arteries to the brain and cause a stroke.

Side Effect - An undesired reaction that results from a medication or therapy. For example, heart failure medications can cause side effects such as headaches, nausea, dizziness, kidney complications and low blood pressure.

Silent Ischemia - Episodes of ischemia that aren't accompanied by pain.

Single Photon Emission Computed Tomography (SPECT) - A nuclear imaging technique that involves injecting a radioactive liquid into the blood, then taking a series of pictures around the chest. SPECT is used to examine blood flow in the heart and to determine how well the heart is pumping. It is also used to diagnose coronary artery disease (CAD).

Sinoatrial (SA) or Sinus Node - Called the "natural pacemaker" of the heart, the SA is located in the right atrium (upper chamber) of the heart. It initiates the heart's electrical activity, stimulating muscle contraction, which pumps blood to the body. (See Pacemaker)

Sinus Rhythm - The normal heart rate and rhythm of the heart. The heart rate during normal sinus rhythm is 60 to 100 beats per minute (BPM).

Social Worker - Within the hospital setting, a person specially trained to counsel and assist in the emotional, social, environmental and financial needs of the heart patient and family. This person often interacts as a liaison of need, working closely with medical staff and the family, both during and after hospitalization.

Sodium (Na) - A mineral that, together with potassium and calcium, regulates the body's water balance, maintains normal heart rhythm and is responsible for nerve impulse conduction and muscle contraction. In general, the more sodium consumed, the more water is retained in the body. Excessive intake of sodium from food contributes to high blood pressure in some people. In people who already have high blood pressure, too much sodium may increase the risk of stroke, heart disease and kidney damage. Table salt (sodium chloride) is nearly half sodium. The recommended daily intake of sodium is less than 2300 mg, or slightly less than one teaspoon.

Spasm - The sudden, temporary or prolonged contraction of a muscle or artery.

Sphygmomanometer (Blood Pressure Monitor) - An instrument for measuring blood pressure.

Stable Angina - Predictable chest discomfort that usually occurs during exertion (such as running to catch a bus) or under mental or emotional stress. Normally the chest discomfort is relieved with rest, nitroglycerin or both.

Stages of Heart Failure - Developed by the American Heart Association and American College of Cardiology in 2001, this staging system is designed to evaluate the development and progression of heart failure. Stages A and B represent people who have not yet developed heart failure, but are at high risk to do so because of coronary artery disease (CAD), high blood pressure, diabetes or other predisposing risk factor. Stage C includes patients with past or current symptoms of heart failure who have structural heart disease. Stage D includes patients who have advanced heart failure that is difficult to manage with standard treatment.

Statins - A group of drugs used to reduce elevated low-density lipoprotein (LDL) or "bad" cholesterol, which is associated with increased risk of cardiovascular disease. They work in the liver to prevent cholesterol from forming. They are also known as HMG CoA reductase inhibitors.

Stenosis - The narrowing or constriction of an opening, such as a blood vessel or heart valve.

Stent Procedure - Using a wire mesh tube (a stent) to prop open an artery that's recently been cleared using angioplasty.

Stethoscope - An instrument for listening to sounds within the body.

"Strep" Infection (Streptococcal Infection) - An infection, usually in the throat, resulting from streptococcus bacteria.

Stress - Bodily or mental tension resulting from a person's response to physical, chemical or emotional factors. Stress can refer to physical exertion as well as mental anxiety.

Stress Test - (See Exercise Stress Test)

Stroke (Apoplexy, Cerebrovascular Accident) - An interruption of blood flow to the brain causing paralysis, slurred speech and/or altered brain function. It may be caused by a blood clot blocking circulation or by bleeding into brain tissue causing tissue damage. A stroke can happen when a blood vessel carrying blood to the brain is blocked by a blood clot. This is called an ischemic stroke. A hemorrhagic stroke occurs when a blood vessel breaks open due to trauma or an aneurysm ruptures causing blood to leak into the brain.

Subaortic Stenosis - A congenital heart defect in which the left ventricle is narrowed (stenosis) just below the aortic valve, which blood passes through to go into the aorta. This limits the flow of blood out of the left ventricle. The defect can also be due to a form of cardiomyopathy. Treatment depends on the cause and severity of the narrowing and includes drugs and surgery. People with subaortic stenosis, before and after treatment, are at risk for infection within the aorta or the heart valves (endocarditis). To help prevent this, they should take antibiotics before certain dental and surgical procedures.

Subarachnoid Hemorrhage - Bleeding from a blood vessel on the surface of the brain into the space between the brain and the skull. A type of stroke.

Sudden Cardiac Death (SCD, Sudden Death) - SCD is death resulting from the abrupt loss of heart function (cardiac arrest). Death occurs within minutes after the heart stops. SCD due to cardiac arrest may be prevented if CPR (cardiopulmonary resuscitation) is performed and a defibrillator is used to shock the heart and restore a normal heart rhythm within a few minutes. Most of the cardiac arrests that lead to sudden death occur when the electrical impulses in the diseased heart become rapid (ventricular tachycardia) or chaotic (ventricular fibrillation) or both. A heart attack may cause cardiac arrest and sudden cardiac death, but the terms aren't synonymous.

Superior Vena Cava - A major vein that carries blood from the upper body (head, neck, chest and arms) to the heart.

Supraventricular Tachycardia - A condition in which heart tissue in either the upper chambers (atria) or the middle region (above the ventricles) develops pacemaker activity, resulting in an abnormally fast heartbeat.

Swan-Ganz Catheter - A soft catheter with an expandable balloon tip that is used for measuring blood pressure in the pulmonary artery, named for its inventors, Jeremy Swan and William Ganz. (See Pulmonary Artery Catheterization)

Sympathetic Nerve Inhibitors - A class of antihypertensive drugs that reduce blood pressure by inhibiting the sympathetic nerves from constricting blood vessels.

Syncope - Passing out, loss of consciousness or fainting caused by a temporary deficiency of oxygen in the brain.

Systole - The contraction phase of the normal heart cycle during which blood is driven into the aorta and pulmonary artery.

Systolic Blood Pressure - The highest blood pressure measured in the arteries. The pressure of blood inside arteries that occurs during the pumping phase of the heartbeat. It is measured in millimeters of mercury (mmHg) and is the upper number in the standard blood pressure reading.

Systolic Heart Failure - A condition in which the heart pumps with less strength than normal (decreased ejection fraction). As time goes on, the pumping chambers (ventricles) become thin, large and floppy. Because blood cannot be pumped out as well, it backs up into organs. This causes swelling (edema) (particularly noticed in the feet and ankles) and congestion in the lungs. As the disease progresses, the heart is unable to pump enough blood (and oxygen) around the body to meet its needs. This type of heart failure is more common and caused by conditions such as coronary artery disease (CAD), high blood pressure, valvular heart disease and idiopathic cardiomyopathy.

Tachycardia - An abnormally fast heartbeat (more than 100 beats per minute).

Tetralogy of Fallot - A complex, congenital heart defect with four components: ventricular septal defect, pulmonary valve stenosis, muscular right ventricle and the aorta directly over the ventricular septal defect. Blood pumped to the body contains less-than-normal amounts of oxygen. This results in cyanosis, a blue discoloration of the skin. Some infants with severe Tetralogy of Fallot may need an operation to give temporary relief by increasing blood flow to the lungs with a shunt. Most children with this condition have open-heart surgery before school age. After surgery the long-term outlook varies, depending largely on how severe the defects were before surgery. Lifelong medical follow-up is needed. People with Tetralogy of Fallot, before and after treatment, are at risk for getting an infection within the aorta or the heart valves (endocarditis). To help prevent this, they should take antibiotics before certain dental and surgical procedures.

Thallium Stress Test - A type of nuclear scanning test similar to a routine exercise stress test but with images. This test shows how well the heart muscle is supplied (perfused) with blood. It uses a radioactive substance called thallium that's injected into the bloodstream when the patient is at maximum level of exercise. Then pictures are taken of the heart's muscle cells using a special (gamma) camera. Patients who cannot physically exercise will receive a medication to increase blood flow in the heart as if they were exercising. The radionuclide tracers cardiolite and myoview can also be used instead of thallium for this test. (Also known as Myocardial Perfusion Imaging (MPI), Radionuclide Stress Test and Nuclear Stress Test.)

Thoracoscopic Surgery - Similar to arthroscopic surgery for joint surgery or laparoscopic surgery in the abdomen, thoracoscopic surgery is performed by using small incisions and video cameras to do procedures typically done through larger open incisions.

Three-dimensional ("3-D") Echocardiography - Current echo technology allows the echo to be viewed in only two dimensions. Three-dimensional echocardiography allows the physician to "reconstruct" the heart and view the structural defects at any angle.

Thrombolysis - The breaking up of a blood clot.

Thrombosis - The formation or presence of a blood clot (thrombus) inside a blood vessel or chamber of the heart.

Thrombus - A blood clot that forms inside a blood vessel or chamber of the heart.

Tissue Plasminogen Activator (tPA) - One of several clot-dissolving (thrombolytic) drugs used during a heart attack or stroke to restore blood flow in a blocked artery. To be effective, it must be given within a few hours after symptoms begin. For a person having an acute heart attack, tPA works by dissolving a major clot quickly. By dissolving the clot, the blood is able to start flowing again to that area of the heart. If the blood flow to the heart is started again rapidly, it may prevent long-term damage to the heart muscle and may even stop an event that could have been fatal.

Total Anomalous Pulmonary Venous Connection (Total Anomalous Pulmonary Venous Return TAPVR) - A congenital heart defect in which the pulmonary veins bring oxygenated (red) blood from the lungs back to the right side of the heart rather than the left side of the heart where it should be. The blood passing through the aorta to the body doesn't have enough oxygen, which causes the child to look blue (cyanotic). This condition requires surgical correction, the timing of which depends on how sick the patient is. The surgery may be done in the newborn period if the infant has severe systems or at some time during the first six months of life. It is an open-heart procedure.

Trans Fats (Trans Fatty Acids) - A fat that is formed when liquid vegetable oils go through a chemical process called hydrogenation in which hydrogen is added to make the oils more solid. Hydrogenated vegetable fats are used by food processors because they allow longer shelf life and give food desirable taste, shape and texture. The majority of trans fat can be found in shortenings, stick (or hard) margarine, cookies, crackers, snack foods, fried foods (including fried fast food), doughnuts, pastries, baked goods and other processed foods made with or fried in partially hydrogenated oils. Some trans fat is found naturally in small amounts in various meat and dairy products. Evidence suggests that consuming trans fat can raise LDL ("bad") cholesterol levels and lower HDL ("good") cholesterol levels.

Transesophageal Echocardiography (TEE) - An ultrasound technique in which the ultrasound probe (about as large as a pinky finger) is placed in the esophagus to "look" at the heart from behind. Transesophageal echocardiography is much more sensitive than transthoracic (across the chest) echocardiography, as overlying structures (bone and lungs) do not obscure the view. This technique requires sedation in almost all cases.

Transient Ischemic Attack (TIA) - Known as a "mini stroke", TIA is caused by a temporary disturbance of blood supply to an area of the brain. It lasts for only for a short time. TIA is an extremely important indicator of future stroke. The age of onset varies, but incidence rises dramatically after age 50. TIA is more common among men and African Americans. Also called a "little stroke".

Transmyocardial Revascularization (TMR) - A procedure used to relieve severe angina or chest pain in very ill patients who aren't candidates for bypass surgery or angioplasty. In this procedure, a surgeon makes an incision on the left breast to expose the heart. Then, using a laser, the surgeon drills a series of holes (20 to 40 mm wide) from the outside of the heart into the heart's pumping chamber. In some patients TMR is combined with bypass surgery. How TMR reduces angina still isn't fully understood. The laser may stimulate new blood vessels to grow, called angiogenesis, or it may destroy nerve fibers to the heart, making patients unable to feel their chest pain.

Transposition of the Great Arteries - A congenital heart defect in which the positions of the pulmonary artery and the aorta are reversed. The aorta receives the oxygen-poor blood from the right ventricle, but it's carried back to the body without receiving more oxygen. Likewise, the pulmonary artery receives the oxygen-rich blood from the left ventricle but carries it back to the lungs. Most babies with transposition of the great arteries are extremely blue (cyanotic) soon after birth. Two general types of surgery may be used to help fix the transposition, but the long-term outlook depends largely on how severe the defects were before surgery. Lifelong follow-up is needed. People with transposition of the great arteries, before and after treatment, are at risk for getting an infection on the heart's walls or valves (endocarditis). To help prevent this, they should take antibiotics before certain dental and surgical procedures.

Tricuspid Atresia - A congenital heart defect in which there's no tricuspid valve. That means no blood can flow from the right atrium to the right ventricle. As a result, the right ventricle is small and not fully developed. Often a surgical shunting procedure is needed to increase blood flow to the lungs. Some children with tricuspid atresia have too much blood flowing to the lungs. They may need a procedure (pulmonary artery banding) to reduce blood flow to the lungs. Other children with tricuspid atresia may have a more functional repair (Fontan procedure) in which a connection is created between the right atrium and pulmonary artery, and the atrial defect is closed. Children with tricuspid atresia require lifelong follow-up by a cardiologist. People with tricuspid atresia, before and after treatment, are at risk for getting an infection of the valves (endocarditis). To help prevent this they should take antibiotics before certain dental and surgical procedures.

Tricuspid Valve - The heart valve between the right atrium and the right ventricle. It has three flaps (cusps).

Triglyceride - Triglycerides are the chemical form in which most fat exists in food as well as in the body. They're also present in blood plasma and, in association with cholesterol, form the plasma lipids. They can be made in the body from energy sources such as carbohydrates or come from fats eaten in foods. Calories ingested in a meal and not used immediately by tissues are converted to triglycerides and transported to fat cells to be stored. Hormones regulate the release of triglycerides from fat tissue so they meet the body's needs for energy between meals. The normal level of triglycerides is less than 150 mg/dL. Excess triglycerides has been linked to the occurrence of coronary artery disease (CAD).

Troponins - Proteins found in heart muscle. Blood tests for troponins can detect heart muscle injury.

Truncus Arteriosus - A complex congenital heart defect where only one artery arises from the heart and forms the aorta and pulmonary artery. Surgery for this condition usually is required early in life. Children with truncus arteriosus need lifelong follow-up to see how well the heart is working. People with truncus arteriosus, before and after treatment, are at risk for getting an infection on the heart's walls or valves (endocarditis). To help prevent this, they should take antibiotics before certain dental and surgical procedures.

Ultrafast®CT - (See Electron-Beam Computed Tomography)

Ultrasound - High-frequency sound vibrations, not audible to the human ear, used in medical diagnosis.

Unstable Angina - Chest pain or discomfort that's unexpected and usually occurs while at rest. The discomfort may be more severe and prolonged than typical angina or be the first time a person has angina. Unstable angina is an acute coronary syndrome and should be treated as an emergency.

Vaccine - Weakened or dead germs, given by injection, that protect against infectious disease. People with heart failure should receive a yearly influenza vaccine and a one-time pneumococcal vaccine (to guard against pneumonia).

Variant Angina Pectoris (or Prinzmetal's Angina) - Attacks of chest pain due to coronary artery spasm that occur almost exclusively when a person is at rest.

Vascular - Pertaining to blood vessels.

Vasoconstriction - A narrowing of a blood vessel, causing decreased blood flow to a part of the body.

Vasodilators - A group of drugs that cause the muscle in the walls of the blood vessels (especially the arterioles) to relax, allowing the vessels to dilate. Nitroglycerin tablets are a form of vasodilator.

Vein - One of a series of vessels that carries blood from various parts of the body back to the heart.

Ventricle - One of the two lower chambers of the heart that receive blood from the atria (upper chambers). The right ventricle pumps blood to the lungs and the left ventricle pumps blood to the rest of the body.

Ventricular Fibrillation (VF) - A severely abnormal heart rhythm (arrhythmia) that, unless treated immediately, causes death. During VF, the ventricles contract independently of the atria and in a disorganized manner. The most common cause of VF is a heart attack, but VF can occur whenever the heart muscle is affected by a poor supply of oxygen (ischemia) or by specific heart disorders. Other conditions that can lead to VF include congenital heart disease, heart surgery, heart muscle disease, electrocution or accidents involving direct trauma to the heart. VF is the main cause of sudden cardiac death (SCD). While many VF patients have no previous history of heart disease, they do have risk factors for cardiovascular disease, such as smoking, hypertension and diabetes.

Ventricular Septal Defect (VSD) - A congenital heart defect in which one or more holes exist in the muscular wall that separates the heart's right and left ventricles (lower chambers). It is the most common congenital heart defect. As with most types of congenital heart disease, no one knows what causes VSDs. This defect often occurs along with other congenital heart malformations. In adults, VSD is a rare but serious complication of heart attacks. These holes are related to the heart attack and do not result from a birth defect.

Ventricular Tachycardia - A very fast, abnormal heartbeat (arrhythmia) initiated within the heart's lower chambers (ventricles). VT is potentially lethal if the heart becomes unable to pump adequate blood through the body. VT can occur in the absence of apparent heart disease. It can also develop as a complication of a heart attack, following heart disease, surgery or with cardiomyopathy, valvular heart disease or myocarditis. Healed scar tissue from heart attacks can lead to VT days, months or years after the heart attack. VT can also result from anti-arrhythmic medications or from altered blood chemistries (such as a low potassium level), pH (acid-base) changes or insufficient oxygenation. VT is classified as nonsustained (often defined as lasting less than 30 seconds) or sustained. "Torsade de pointes" is a form of VT with a specific variation in the conduction of the ventricular stimulus.

Venules - Small veins, the blood vessels that carry blood back to the heart and lungs.

Vertebral Artery - One type of major blood vessel in the neck carrying blood from the heart to the brain. The other type is carotid artery.

Wolff-Parkinson White Syndrome (WPW) - A condition in which the heart beats too fast due to abnormal, extra electrical pathways between the heart's upper and lower chambers. In a normal heart, the electrical signal moves from the heart's upper chambers (the atria) to the lower chambers (the ventricles), causing the heart to beat. If there's an extra conduction pathway, the electrical signal may cause a rapid heart rate (tachycardia). WPW can be present at birth (congenital), but symptoms can appear at any time. More women than men are diagnosed with WPW. Treatments include medications and some surgical procedures.