Glossary of Heart & Vascular Terms

A to Z Glossary for Heart & Vascular Care
Select the first letter of the term



Cardiac ablation uses a form of energy to physically destroy or “ablate” a small section of damaged heart tissues that causes or contributes to some types of tachycardia (fast heartbeat). Ablation is either performed surgically or by using an electrode catheter, called catheter ablation.


An abnormal widening or ballooning-out of the wall of an artery, a vein or the heart due to weakening of the wall by disease, injury or abnormality. Common locations for aneurysms including the aorta (the major artery leading away from the heart), brain (cerebral aneurysm, leg, intestine and splenic artery.

Angina Pectoris

Medical term for chest pain or discomfort due to coronary heart disease. Angina is a symptom of a condition called myocardial ischemia. It occurs when the heart muscle does not get as much blood as it needs for a given level of work. Stable angina refers to “predictable” chest discomfort such as that associated with physical exertion or mental or emotional stress. Unstable angina refers to unexpected chest pain and usually occurs at rest. It is typically more severe and prolonged. Unstable angina is an acute coronary syndrome and should be treated as an emergency.


The creation of blood vessels. The body created small blood vessels called “collaterals” to help compensate for reduced blood flow.


An X-ray test used to detect and diagnose diseases of the blood vessels, such as weakening of the vessel walls and the narrowing or blocking of vessels, and to examine the chambers of the heart. The X-ray is taken after the vessels have been injected with a substance (dye) that allows them to be seen on film. The pictures are called angiograms. Coronary angiography is done during a cardiac catheterization.


A medical procedure in which a balloon is used to open narrowed or blocked coronary arteries. It is not considered a type of surgery. A catheter with a deflated balloon on its tip is passed into the narrowed artery segment, the balloon is inflated and the narrowed segment widened. Then, the balloon is deflated and the catheter is removed.

Ankle-Brachial Index (ABI) Test

A painless exam that compares the blood pressure in the feet to the blood pressure in the arms to determine how well the blood is flowing. It is used to diagnose peripheral artery disease (PAD).


The great arterial trunk that carries blood from the heart to be distributed by branch arteries through the body.

Aortic Stenosis

The narrowing or obstruction of the heart's aortic valve, which prevents it from opening properly and blocks the flow of blood from the left ventricle to the aorta. Aortic stenosis can either be congenital or acquired later in life.

Aortic Valve

The heart valve between the left ventricle and the aorta.


Any heart rate or rhythm disorder. The heart either beats too quickly, too slowly or with an irregular pattern. When the heart beats faster than normal, it is called tachycardia. When the heart beats too slowly, it is called bradycardia.


A test where dye visible to X-rays is injected into the bloodstream to check for artery damage, narrowing or blockage. It is performed during cardiac catheterization.


Small branches of an artery. When they contract, they increase resistance to blood flow and blood pressure in the arteries increase.


Hardening of the arteries. It can occur due to fatty deposits on the inner lining of the arteries, called atherosclerosis, calcification of the wall of the arteries, or thickening of the muscular wall of the arteries from chronic high blood pressure.


One of a series of vessels that carry oxygenated blood from the heart to various parts of the body.


Absence of a heartbeat.


Procedure to remove plaque from arteries. It can be performed using a balloon-tipped catheter (angioplasty), a laser, a drill-tipped catheter or conventional surgery.


Narrowing of the arteries due to the buildup of plaques made of cholesterol.


A form of arteriosclerosis. The progressive narrowing and hardening of the arteries over time. It occurs with aging, but other risk factors—such as high cholesterol, high blood pressure, smoking, diabetes and family history also cause atherosclerosis.


The heart’s two upper chambers that pump blood into the ventricles.

Atrial Fibrillation

A heart rhythm and heart rate disorder in which the heart’s atria quiver rapidly and empty blood into the heart’s ventricles in a disorganized manner.

Atrial Flutter

A very rapid beat of the atria. Considered a serious and potentially unstable heart rhythm.

Atrial Septal Defect

A congenital heart defect where the wall that separate the heart’s atria is defective.

Atrioventricular (AV) Canal Defect

A congenital heart defect where there is a hole in the wall (septum) between the left and right chambers of the heart.

Atrioventricular (AV) Node

The AV node is one of the major elements in the cardiac conduction system, which controls the heart rate and rhythm.


Either of the heart’s two upper chambers where blood collects before being passed to the ventricles.


Bicuspid Aortic Valve

A congenital heart defect in which the aortic valve has two flaps instead of three, which can lead to narrowing and leaking of the aortic valve.

Blood Pressure

The pressure exerted by the heart against the walls of the arteries.

Blood Vessels

Hollow tubes that carry blood from the heart and lungs to every cell in the body and back to the heart and lungs.

Body Fat Measurement (Body Composition)

Determining the percent of fat to lean body mass using measures of height, weight, and skinfold thickness.

Body Mass Index (BMI)

Body Mass Index or BMI is an estimate of obesity using a ratio of height to weight. A BMI score of less than 18.5 is considered underweight; a score of 18.5 to 24.0 is considered normal weight; a score of 25.0 to 29.0 is considered overweight; and a score of 30.0 and above is considered obese.


Slowness of the heart rate (less than 60 beats per minute).


C-Reactive Protein

A protein that increases in the blood in response to inflammation. It is a marker for increased risk for heart disease and is often elevated years before a person has a first heart attack or stroke.


Pertaining to the heart.

Cardiac Arrest

A sudden loss of heart function. Occurs when the electrical impulses in the diseased heart become rapid or chaotic or both. The irregular heart rhythm causes the heart to suddenly stop beating.

Cardiac Care Unit

A specialized facility that is equipped with monitoring devices and specially trained staff for heart patients.

Cardiac Catheterization

The process of examining the heart by guiding a catheter into a vein or artery and passing it into the heart and coronary arteries. Aniography and angioplasty are performed during a cardiac catheterization.

Cardiac Computed Tomography (CT) Scan

An X-ray imaging technique that uses a computer to produce a cross-sectional image of the chest or the brain.

Cardiac Enzymes

Enzymes in the body that are released into the bloodstream when heart muscle cells are damaged.

Cardiac Positron Emission Tomography (PET)

A noninvasive, nuclear imaging technique that uses cross-sectional images and radioactive tracers to study how the heart tissue works.

Cardiac Rehabilitation

A medically supervised program to help patients recover quickly and improve their overall physical and mental functioning. The goal is to reduce the risk of another cardiac event or to keep an existing heart condition from getting worse. Research shows that patients who participate in rehabilitation programs have a higher survival rate and a better quality of life.

Cardiac Resynchronization (Biventricular Pacing)

A treatment for heart failure using a biventricular pacemaker, which is implanted in the chest. Both ventricles are paced to contract at the same time, which can reduce the symptoms of heart failure.


A doctor who diagnoses and treats heart problems.


The study of the heart and its functions in health and disease.


A disease in the heart consisting of inflammation and reduced function of heart muscle. There are three main types: dilated, hypertrophic and restrictive. Treatment varies depending on the underlying cause.


A procedure that takes muscles from the back or abdomen and wraps them around the heart. The muscle is stimulated by a device similar to a pacemaker and may boost the heart's pumping action.

Cardiopulmonary Bypass (Heart/Lung Machine)

A procedure that circulates and oxygenates blood during heart surgery. Blood from the heart and lungs is diverted through a heart/lung machine and the return of oxygenated blood to the aorta.


Pertaining to the heart and blood vessels.


When an electrical shock is delivered to a person’s heart to quickly revert an arrhythmia back to normal. Can be performed with an automatic external defibrillator (AED) or an implantable cardioverter defibrillator (ICD).

Carotid Artery

One type of major artery in the neck that carries blood from the heart to the brain.

Carotid Artery Disease

A carotid artery narrowed from plaque buildup. A major factor for ischemic stroke.

Carotid Artery Stent

A wire mesh tube that is inserted during carotid angioplasty to hold an artery open. It permanently stays in place, improving blood flow.

Carotid Phonoangiography

A test that uses a microphone on the neck to record sounds and detect blockages that are caused by carotid artery disease.


A soft, waxy substance found among the fats in the bloodstream and in all the body's cells. It is a constituent of all animal fats and oils. Cholesterol is an important part of a healthy body since it is used to form cell membranes, some hormones, and other needed tissues. A high level of cholesterol in the blood, however, is a major risk factor for heart disease.

Closed Heart Surgery

An operation on the heart without the need for cardiopulmonary bypass.

Congenital Heart Disease

An abnormality that is present at birth that affects the heart.

Congestive Heart Failure

An outdated term for heart failure, the inability of the heart to pump out all the blood that returns to it.

Coronary Arteries

Two arteries arising from the aorta that arch down over the top of the heart, branch and provide blood to the heart muscle.

Coronary Artery Bypass Graft (Bypass Surgery or CABG)

Surgery that re-routes blood around clogged coronary arteries and improves blood supply and oxygenation to heart muscle.

Coronary Artery Disease

Conditions that cause narrowing of the arteries, reducing blood flow to the heart muscle.

Coronary Occlusion (Thrombosis)

An obstruction of a coronary artery that hinders blood flow to some part of the heart muscle and causes a heart attack.

Coronary Occlusion (Thrombosis)




The use of a defibrillator to give an electric shock to the heart to regulate an abnormal heart rhythm.


A mood disorder marked by loss of interest or pleasure in living. Symptoms include persistent sadness, hopelessness or tearfulness; persistent fatigue; persistent feelings of guilt or self-criticism; a sense of worthlessness; inability to concentrate; decreased interest in daily activities; changes in appetite or body weight; insomnia or excessive sleep.


A disease caused by increased blood sugar. Increased blood sugar is caused by the body not making insulin (Type I diabetes) or the body’s inability to secrete and/or use insulin (Type II diabetes). Diabetes is a risk factor for heart disease.

Diastolic Blood Pressure

The lowest blood pressure measured in the arteries that occurs when the heart muscle relaxes between beats.

Diastolic Dysfunction

Abnormal function of the heart during its relaxation phase (diastole).

Diastolic Heart Failure

A condition where the ventricles become thick, grow stiff and cannot relax to fill the hearts ventricles with blood.

Doppler Ultrasound

A test using high-frequency sound waves to detect blockages in an artery and evaluate blood flow.


Difficult or labored breathing that is often caused by heart conditions.


Echocardiography (EKG)

A diagnostic method where a hand-held device is placed on the chest and high-frequency sound waves are used to produce images of the heart’s size, structure and motion. It helps provide information about arrhythmias and overall heart health.

Electron-Beam Computed Tomography

 A high-speed form of X-ray imaging technology that is used to evaluate structures sand functions in the heart and measure calcium deposits in the coronary arteries.

Electrophysiologic Testing

An invasive diagnostic study of the electrical circuitry of the heart. It may be used for diagnosing fast or slow heart rhythms. Temporary electrode catheters are positioned in the heart’s atria and/or ventricles and at strategic locations along the conduction system. They record the electrical signals and “map” the spread of electrical impulses during each heartbeat.


Surgical removal of plaque deposits or blood clots in the lining of an artery.


An inflammation of the heart’s inner lining or valves, usually caused by bacterial infection.


Physical activities to maintain or increase muscle tone and strength. Physical exercise for 30 minutes on most, if not all, days of the week is recommended to prevent heart disease.

Exercise Stress Test (Treadmill Test)

A medical test performed to evaluate arterial blood flow to the myocardium (heart muscle) during physical exercise compared to blood flow while at rest.



Fast, uncoordinated contractions of individual heart muscle fibers. The heart chamber involved cannot contract all at once and pumps blood ineffectively, if at all.


Glucose (Blood Sugar)

A simple sugar that is an end product of carbohydrate digestion in the human body. Healthy people maintain a glucose level of between 70 and 110 mg/dl.


HDL Cholesterol

Often called “good” cholesterol because a high level seems to protect again heart attack and other cardiovascular conditions.

Heart Attack

See Myocardial Infarction.

Heart Disease

Diseases of the heart muscle, heart valves or the coronary arteries of the heart.

Heart Disease 10-year Risk Assessment

A tool utilized to estimate a patient’s potential to have a heart attack or coronary death based on personal risk factors. The tool utilizes data from the Framingham Heart Study.

Heart Failure

The inability of the heart to pump enough blood to meet the needs of the body’s other organs. The most common causes of heart failure are coronary artery disease, previous heart attack and hypertension. People who are overweight, have diabetes, smoke cigarettes, abuse alcohol or use cocaine are also at higher risk for heart failure.

Heart Murmur


Heart Valve

There are four valves in the heart that control the direction of blood flow through the heart by opening and closing with each heartbeat. The valves permit the blood to flow in one direction. The four valves are the tricuspid valve, pulmonary valve, mitral valve and aortic valve.

Heart Valve Replacement Surgery

Open-heart surgery to replace a defective or diseased heart valve. Replacement heart valves are either natural (biologic) or artificial (mechanical).

Hemoglobin A1C

A blood test that is a good indicator as to how well a woman has controlled her diabetes in the previous five to six weeks. A level less than 7 percent is recommended.

Holter Monitor

A battery-operated, portable device that measures and records the heart’s electrical activity continuously for 24 to 48 hours or longer.




High levels of blood cholesterol, which is a major risk factor for heart disease, heart attack and stroke.


A chronic increase in blood pressure above normal range. Optimal blood pressure is less than 120/80 mm Hg. Blood pressure of 120-139/80-89 mm Hg are considered prehypertension. High blood pressure is 140/90 mm Hg or higher. Hypertension increases the risk for heart attack, angina, stroke, kidney failure and peripheral artery disease and may also increase the risk of atherosclerosis and heart failure.


High levels of triglycerides in the blood. A high triglyceride level combined with low HDL cholesterol or high LDL cholesterol seems to speed up atherosclerosis. A normal triglyceride level is less than 150 mg/dL.


Abnormally low blood pressure, measuring at or below 90/60 mm Hg. Some people have low blood pressure with no symptoms and their low readings are normal. In others, blood pressure drops below normal because of some event or medical condition and can cause dizziness and fainting.


Implantable Cardioverter/Defibrillator (ICD)

An internal defibrillator used to monitor the heart rhythm and detect overly rapid arrhythmias. It corrects the heart rhythm by delivering precisely calibrated and timed electrical shocks to restore a normal heartbeat.

Inferior Vena Cava

A major vein that carries blood from the lower body (legs and abdomen) to the heart.

Intermittent Claudication

A cramping sensation in the legs that is present during exercise or walking and occurs as a result of decreased oxygen supply.

Intraaortic Balloon Pump

A device used in treating severe left ventricular failure. The device assists the left ventricle in pumping and increases cardiac output, which helps relieve pulmonary congestion and heart failure.


Reduced blood flow to an organ, usually due to a constricted or blocked artery.


Laser Angioplasty

A technique used to open coronary arteries blocked by plaque. A catheter with a laser at its tip is inserted into an artery and advanced to the blockage. When the laser is in position, it emits pulsating beams of light that vaporize the plaque.

LDL Cholesterol

Called the “bad” cholesterol, LDL is the major cholesterol carrier in the blood. Too much of this cholesterol can slowly build up in the walls of the arteries that lead to the heart and brain. Together with other substances it can form plaque that can clog those arteries.

Left-ventricular Assist Device

A battery operated mechanical pump that is surgically implanted and used to aid the natural pumping action of the heart’s left ventricle.


A fatty substance that is insoluble in blood. Cholesterol, cholesterol compounds, and triglycerides are all lipids.

Lipid Testing

Also known as cholesterol testing, lipid testing is taken when cholesterol levels in the blood are tested. This includes testing HDL, LDL and triglycerides and sometimes Lp(a), a genetic variation of LDL.


The combination of a lipid surrounded by a protein, which allows the fat to travel in the blood.

Long QT Syndrome

A condition that affects the heart’s electrical system and may cause fast and chaotic heartbeats. It can cause fainting and in some cases cardiac arrest.

Lp(a) Cholesterol

A genetic variation of LDL cholesterol that resembles LDL in composition with an abnormal protein, called “little a,” attached. A high level of Lp(a) is a risk factor for premature heart disease.


Magnetic Resonance Imaging

An imaging procedure that uses powerful magnets to look inside the body. It scomputer-generated pictures can image the heart muscle and evaluate different heart problems.

Maze Procedure

A surgical procedure performed on the left or right atria to control atrial fibrillation and/or atrial flutter. Incisions are made to block the path of the arrhythmia.

Metabolic Syndrome

A group of metabolic risk factors in one person. Metabolic syndrome increases your risk of having a heart attack or stroke. You are also at increased risk of developing diabetes within five to 15 years after being diagnosed with metabolic syndrome.

Minimally-Invasive Heart Surgery

An alternative to coronary artery bypass surgery, where small incisions are made in the chest and arteries or veins from the leg are attached to the heart to bypass the clogged coronary artery or arteries. Benefits of minimally-invasive heart surgery include reduced incision size and less scarring. Minimally-invasive surgery also offers the potential for a quicker recovery time, shorter hospital stay, reduced risk of infection, less bleeding and less pain and trauma.

Mitral Valve

A dual “flap” in the heart located between the heart’s left upper chamber (atrium) and left lower chamber (ventricle) that opens and closes.

Mitral Valve Prolapse

 A common heart disorder that occurs when the mitral valve doesn't close properly. This sometimes lets a small amount of blood leak backward through the valve and may cause a heart murmur.

Mitral Valve Stenosis

A narrowing of the mitral valve, which limits the forward flow of blood and can cause a backup of blood and fluid in the lungs. It’s usually caused by rheumatic fever, which results from untreated strep infections, which can scar the mitral valve. It is a treatable condition—treatment depends on its progression and signs and symptoms.

Myocardial Infarction

Also known as a heart attack: the death of or damage to part of the heart muscle due to an insufficient blood supply. It occurs when one of the coronary arteries that supply blood to the heart muscle is blocked. The blockage is usually caused by plaque buildup from atherosclerosis.

Myocardial Ischemia

A condition where not enough blood flows to the heart muscle. Symptoms include angina and decreased exercise tolerance.


Inflammation of the heart muscle. It is an uncommon disorder that is usually caused by viral infections such as coxsackie virus, adenovirus and echovirus. It may also occur during or after various viral, bacterial or parasitic infections.


The muscular center layer of the heart that is responsible for the heart’s pumping action and contracts to pump blood out of the heart and then relaxes as the heart refills with returning blood.


Occluded Artery

An artery in which blood flow has been impaired by a blockage.



An artificial pacemaker is an electrical device that regulates the speed and rhythm of the heartbeat. Usually, these devices are used for hearts that beat too slowly. They are powered through batteries and usually last many years.


The sensation of the heart beating quickly or irregularly.

Percutaneous Transluminal Coronary Angioplasty

See angioplasty.


Blood flow.


A disorder caused by inflammation of the pericardium. It’s usually a complication of a viral, bacterial or fungal infection and can also result from a heart attack, cancer, radiation treatment, injury or surgery.


The outer, fibrous “sac” that surrounds the heart.

Peripheral Artery Disease

A common circulatory problem in which narrowed arteries reduce the blood flow to the legs and feet. Symptoms include pain in the legs when exercising that goes away when the activity is stopped.


Also called atheroma, a buildup of cholesterol in the inside wall of the blood vessels.


A condition where blood glucose (blood sugar) levels are consistently higher than normal but not high enough to be called diabetes.

Pulmonary Artery Catheterization

Used to evaluate primary pulmonary hypertension. The doctor places a thin, flexible tube through an artery or vein in the arm, leg or neck and threads it into the right ventricle and pulmonary artery. It measures the pressure of the pulmonary artery and helps physicians determine appropriate treatment.

Pulmonary Edema

Fluid buildup in the lungs usually due to mitral valve stenosis or left ventricular failure. Symptoms include difficulty breathing, coughing up blood, excessive sweating, anxiety and pale skin.

Pulmonary Veins

Four veins that return blood from the lungs to the heart. They empty into the atrium of the heart.

Pulmonic Valve

The heart valve between the right ventricle and the pulmonary artery. It has three flaps.



The leakage that results when a heart valve that does not 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. It can include clot-dissolving medications, balloon angioplasty or surgery.


A renarrowing of an artery after angioplasty, stent or bypass surgery. About one-third of patients who undergo angioplasty have restenosis within approximately 6 months of the procedure. Restenosed arteries may have to undergo another angioplasty.

Right Heart Ventriculography

A test used to study of the right chambers of the heart. It obtains measurements of pressure, oxygen and cardiac output through a catheter.


Saturated Fats

Fat found in all foods from animals—including butter, cheese, whole milk, ice cream, cream and fatty meats—and some plants, such as coconut, palm and palm kernel oils. They are the biggest causes of high LDL cholesterol.


The muscular wall dividing the chambers on the heart’s left side from the chambers on the right side.


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.


A surgically created connection designed to increase the delivery of blood to the lungs. They are also used in bypass surgery and to drain fluids from the body.

Silent Ischemia

Episodes of ischemia that are not accompanied by any pain.

Single Photo Emission Computed Tomography

A nuclear imaging technique that involves injecting a radioactive liquid into the blood, then taking a series of pictures around the chest. It is used to examine blood flow in the heart and determine how well the heart is pumping. It also can diagnose coronary artery disease.

Sinoatrial or Sinus Node

Called the “natural pacemaker” of the heart, it is located in the right atrium of the heart. It initiates the heart’s electrical activity, stimulating muscle contraction, which pumps blood to the body.

Sinus Rhythm

The normal heart rate and rhythm of the heart, which is 60 to 100 beats per minute.

Stable Angina

Predictable chest discomfort that usually occurs during exertion or under mental or emotional stress. Usually it is relieved with rest, nitroglycerin or both.



Stent Procedure

A wire mesh tube, called a stent, is used to prop open an artery that has been cleared from angioplasty.


Perceptions, emotions, anxieties, and interpersonal, social or economic events that are considered threatening to one’s physical health, personal safety or well being.

Sudden Cardiac Death

Death resulting from cardiac arrest, or the sudden loss of heart function. It can be prevented if cardiopulmonary resuscitation is performed and a defibrillator is used to shock the heart rhythm back to normal within a few minutes.

Superior Vena Cava

 A major vein carrying blood from the upper body to heart.

Supraventricular Tachycardia

Rapid rhythm of the heart in which the origin of the electrical signal is either the atria or the AV node. These rhythms, by definition, are either initiated or maintained by the atria or the AV node. This is in contrast to the more dangerous ventricular tachycardias, which are rapid rhythms that originate from the ventricles of the heart (below the atria or AV node).

Systolic Blood Pressure

The highest blood pressure measured in the arteries, it is the upper number in the standard blood pressure reading. It is the pressure of blood inside arteries that occurs during the pumping phase of the heartbeat.

Systolic Heart Failure

Occurs when the heart muscle doesn't contract with enough force, so there is not enough oxygen-rich blood to be pumped throughout the body. Doctors can measure how well the heart pumps with each beat to determine if systolic or diastolic dysfunction are present.



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

Thallium Stress Test

A procedure similar to an exercise stress test that determines whether exercise causes a decreased blood flow to the heart muscle. It uses a radioactive substance called thallium that is injected into the bloodstream. Pictures are then taken of the heart’s muscle cells using a special camera.

Thoracoscopic Surgery

A less-invasive form of surgery performed by using small incisions and video cameras.


The format or presence of a blood clot inside a blood vessel or chamber of the heart.

Total Cholesterol

The sum of LDL and HDL cholesterol and triglycerides in the bloodstream.

Trans Fats

A fat formed when liquid vegetable oils go through a chemical process called hydrogenation, in which hydrogen is added to make the oils more solid. Evidence suggests that consuming trans fat can raise LDL and lower HDL cholesterol levels.

Transesophageal Echocardiography

An ultrasound technique in which a small ultrasound probe is placed in the esophagus to look at the heart from behind.

Tricuspid Valve

The heart valve between the right atrium and the right ventricle. It has three flaps, or cusps.


The chemical form in which most fat exists in food as well as in the body. They can be made in the body from energy sources, such as carbohydrates, or come from fats eaten in foods. The normal level of triglycerides is less than 150 mg/dL. Excess levels have been linked to coronary artery disease.


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


Unstable Angina

Chest pain that is 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. It should be treated as an emergency.



Pertaining to blood vessels.


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


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 must be treated immediately. The most common cause is a heart attack, but it can occur whenever the heart muscle is affected by a poor supply of oxygen or by specific heart disorders.

Ventricular Tachycardia

A very fast, abnormal heartbeat initiated within the heart’s lower chambers, or ventricles. It can occur in the absence of apparent heart disease but can also develop as a complication of a heart attack, following heart disease, surgery or with cardiomyopathy, valvular heart disease or myocarditis. It can lead to ventricular fibrillation or sudden death.


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 the carotid artery.