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Glossary H-Z


Glossary Credits: WebMD and the Cleveland Clinic Heart Center.

+ Idiopathic

When the cause of a disease or process is not known.


Idiopathic Hypertrophic Subaortic Stenosis is another term used synonymously with hypertrophic obstructive cardiomyopathy (HOCM). It is an inherited disease of the heart muscle that causes thickening of the heart muscle and other changes to the heart that significantly impair its function. Although the disease is rare, IHSS is the single most common cause of sudden cardiac arrest in seemingly healthy young people.

+ Immunosuppressants

Drugs that are used to keep the body’s immune system from rejecting a transplanted organ, such as the heart, or to slow down the destructive processes of autoimmune disease (where the body’s immune system goes awry and kills normal cells and tissue.)

+ Implantable Cardioverter Defibrillator (ICD)

A surgically inserted electronic device that constantly monitors your heart rate and rhythm. When it detects a very fast, abnormal heart rhythm, it delivers electrical energy to the heart muscle to help the heart to beat in a normal rhythm again.

+ Infarction

Tissue death due to lack of oxygen-rich blood.

+ Inotrope Medication

A medication used to strengthen the heart’s contractions and improve blood circulation.

+ Insulin

A hormone produced by the pancreas that helps the body digest sugar.

+ Intra-aortic Balloon Pump Assist Device (IABP)

A machine that can help the pumping function of the heart. It is usually inserted through an artery in the groin area and threaded backwards into the descending thoracic aorta in the chest. In this location the balloon inflates and deflates in synchrony with the heart in order to aid the blood pumping function of the heart in people with cardiac disease.

+ Intracardiac Tumor

An intracardiac tumor can be any tumor of the heart, either malignant or benign. The most common tumor of the heart is a benign atrial myxoma.

+ Intravascular

Inside a blood vessel.

+ Intravascular Ultrasound (IVUS)

An invasive procedure, performed along with cardiac catheterization. A miniature sound probe (transducer) on the tip of a catheter is threaded through the coronary arteries and, using high-frequency sound waves, produces detailed images of the interior walls of the arteries.

+ Ischemia

Condition in which there is not enough oxygen-rich blood supplied to the heart muscle to meet the heart’s needs.

+ Lead Extraction

A lead is a special wire that delivers energy from a pacemaker or implantable cardioverter defibrillator (ICD) to the heart muscle. A lead extraction is the removal of one or more leads from inside the heart.

+ Leaflets

Thin pieces of tissue or flaps that make up a valve.

+ Left Ventricular Assist Device (LVAD)

A mechanical device placed in people with end-stage heart disease whose hearts do not pump a sufficient amount of blood to keep the body healthy (heart failure). The device aids in the pumping function of the blood.

+ Lipid

Fat circulating in the blood.

+ Lipoprotein

A combination of fat and protein that transports lipids (fats) in the blood.

+ Loop Recorder (Event monitor)

See Event monitor (above)

+ Low-Density Lipoprotein (LDL)

A lipoprotein particle in the blood responsible for depositing cholesterol into the lining of the artery. Known as “bad” cholesterol because high LDL is linked to coronary artery disease.

+ Magnetic Resonance Imaging (MRI)

A test that produces high-quality still and moving pictures of the heart and large blood vessels. MRI uses large magnets and radio-frequency waves to produce pictures of the body’s internal structures. No X-ray exposure is involved. MRI acquires information about the heart as it is beating, creating moving images of the heart throughout its pumping cycle.

+ Mammary Artery (also called thoracic artery)

Artery located in the chest wall and used for coronary artery bypass surgery. Most commonly kept intact at its origin, and sewn to the coronary artery beyond the site of blockage. If the surgeon removes the mammary artery from its origin to use as a bypass graft, it is then called a “free” mammary artery bypass graft.

+ Maze Procedure

A surgical treatment for chronic atrial fibrillation. The surgeon makes multiple incisions in the atrium to form a path or maze through which the impulse can travel to reach the atrioventricular node. After this is done the atrium is sewn back together and a normal rhythm is more easily maintained.

+ Mechanical Valve

In people who require heart valve replacement surgery, it is sometimes desirable to implant a mechanical valve. A mechanical valve is made of artificial parts and functions similarly to a normal heart valve. People who have a mechanical valve implanted must take blood thinners lifelong to prevent blood clots from forming on the mechanical valve.

+ Metabolic Exercise Stress Test (also called metabolic stress test)

A test used to measure the performance of the heart and lungs while they are under physical stress. The test involves walking on a treadmill or pedaling a stationary bike at increasing levels of difficulty, while being closely monitored.

+ Minimally Invasive Heart Surgery

Minimally invasive heart surgery is a technique developed to reduce the trauma associated with open heart surgery. The smaller incision that is used may allow the patient to heal more rapidly and decrease the time to recovery and full activity. It also helps to reduce the pain and discomfort associated with heart surgery.

+ Mitral Insufficiency

A condition where blood in the left ventricle leaks back through the mitral valve into the left atrium and can back up into the lungs. The mitral valve normally opens to allow blood to flow into the left ventricle and then closes, preventing blood from backing up into the atrium during the ventricle’s contraction.

+ Mitral Stenosis

A condition where the mitral valve becomes narrowed or stenotic preventing the easy flow of blood from the left atrium into the left ventricle.

+ Mitral Valve

The valve that lies between the left atrium and left ventricle (main pumping chamber of the heart). This valve allows blood to flow from the left atrium into the left ventricle and then prevents the back flow of blood into the left atrium during ventricular contraction.

+ Morbidity Rate

The percentage of people who have complications from a medical condition or after a procedure or treatment.

+ Mortality Rate

The percentage of deaths associated with a disease or medical treatment.

+ Multigated Acquisition Scan (MUGA scan)

A nuclear scan that evaluates the pumping function of the ventricles.

+ Murmur

Turbulent blood flow across a heart valve creating a “swishing” sound heard by a stethoscope.

+ Myocardial Biopsy (Cardiac biopsy)

An invasive procedure to obtain a small piece of heart muscle tissue that is sent to a laboratory for analysis.

+ Myocardial Infarction (Heart attack)

See heart attack (above).

+ Myocarditis

Inflammation of the myocardium (heart muscle).

+ Myocardium

Heart muscle.

+ Myomectomy

A surgical procedure to remove abnormally thickened heart muscle. Used to treat people with idiopathic hypertrophic subaortic stenosis (IHSS) or HOCM thereby relieving the obstruction to blood flow in the left ventricle during contraction.

+ Nitroglycerin

A medication used to relax and dilate the blood vessels (vasodilator), improving blood flow. Nitroglycerin works very quickly and is the most common vasodilator used to treat angina.

+ Non-Q-Wave MI

A heart attack that does not cause changes known as “Q-waves” on the electrocardiogram (ECG) however, other changes on the ECG are often seen. In addition, chemical markers in the blood indicate that damage has occurred to the heart muscle. In non-Q-wave MI, a clot may block the coronary artery for a period of time, and then break up by itself or collateral circulation may help to restore blood flow to the area of ischemia (lack of blood supply). The size of damage is fairly small; therefore, overall function of the heart is usually maintained.

+ Nuclear Scan

Nuclear imaging is a method of producing images by detecting radiation from different parts of the body after the administration of a radioactive tracer material.

+ Obesity

Excess fat due to eating more calories than used. It is usually defined having a body mass index (BMI-see above) of 25 or higher.

+ Occlusion


+ Off Pump Heart Surgery

Heart surgery done without the use of the cardiopulmonary bypass machine.

+ Pacemaker

A small electronic device is implanted under the skin and sends electrical impulses to the heart muscle to maintain a suitable heart rate and to prevent slow heart rates.

+ Palpitation

A fluttering sensation in the chest that is often related to a missed heart beat or rapid heartbeat.

+ Papillary Muscles

Small muscles that are part of the inside walls of the ventricles and attach to the chordae tendineae.

+ Patency Rate

The likelihood that a vessel will remain open.

+ Pericardiocentesis (pericardial tap)

An invasive procedure that involves using a needle and catheter to remove fluid from the sac around the heart. The fluid may then be sent to a laboratory for tests to look for signs of infection or cancer.

+ Pericardium

The sac that surrounds the heart.

+ Pericarditis

Pericarditis is an inflammation of the pericardium. The pericardium is the sac around the heart.

+ Plaque

Deposits of fats, inflammatory cells, proteins and calcium material along the lining of arteries seen in atherosclerosis. The plaque builds up and narrows the artery

+ Platelets

Components of blood that aid in clotting.

+ Positron Emission Tomography (PET or cardiac viability study)

An imaging procedure that uses radioactive tracers to create 3-dimensional pictures of the tissues inside of the body and can monitor metabolic processes.

+ Premature Ventricular Contractions (PVCs)

An irregular heartbeat in which the lower chambers of the heart (the ventricles) beat before they are supposed to.

+ Prophylaxis

The prevention of disease.

+ Pulmonary Edema

An abnormal swelling of tissue in the lungs due to fluid build-up.

+ Pulmonary Hypertension

Pulmonary hypertension is high blood pressure of the pulmonary arteries.

+ Pulmonic Valve

The last valve through which the blood passes before it enters the pulmonary arterythat lies between the right atrium and from the right ventricle.

+ Pulse Rate

The number of heartbeats per minute. The resting pulse rate for an average adult is between 60 and 80 beats per minute.

+ Q-wave MI

A heart attack that is caused by a prolonged period of blocked blood supply. An area of the heart muscle is affected, causing changes known as “Q-waves” on the ECG as well as chemical markers in the blood.

+ Radial Artery

The radial artery is a blood vessel that carries oxygen-rich blood in the forearm. You can feel the pulse of the radial artery by feeling the inside of the wrist underneath the base of the thumb.

+ Radionuclide Study (MUGA)

See MUGA above.

+ Regurgitation

Leaking or backward flow.

+ Restenosis

The closing or narrowing of an artery that was previously opened by a cardiac procedure such as angioplasty.

+ Rheumatic Fever

Rheumatic fever is an inflammatory reaction ofthat can involve the heart, usually involving the valves as a consequence of streptococcal infection.

+ Rheumatic Heart Disease

Rheumatic fever can lead to a condition known as rheumatic heart disease. This is usually a thickening and stenosis of one or more of the heart valves and often requires surgery to repair or replace the involved valve(s).

+ Rheumatic Valve Disease

Rheumatic valve disease is a consequence of rheumatic fever. Rheumatic valve disease is a thickening and stenosis of one or more of the heart valves and often requires surgery to repair or replace the affected valve(s).

+ Right Ventricular Biopsy

The removal of a small piece of heart tissue from your right ventricle. This tissue sample is studied under a microscope to help your doctor assess your heart muscle.

+ Risk Factor (for heart disease)

Traits people have that are linked to the development and progression of coronary artery disease. There are modifiable risk factors — related to lifestyle and may be changed or controlled — and non-modifiable risk factors — related to aging and genetics and cannot be changed.

+ Rotoblation (Percutaneous Transluminal Rotational Atherectomy or PCRA)

A special catheter, with an acorn-shaped diamond-coated tip, is guided to the point of narrowing in the coronary artery. The tip spins around at a high speed and grinds away the plaque on the artery walls. The microscopic particles are washed safely away in your blood stream and filtered out by the liver and spleen. This process is repeated as needed to allow better blood flow.

+ Saphenous Vein

Vein located in the leg(s) and used for coronary artery bypass surgery. It is surgically removed from the leg and sewn from the aorta to the coronary artery beyond the site of blockage.

+ Septum

The muscular wall separating the right and left sides of the heart.

+ Sestamibi Exercise Stress Test (Sestamibi stress test, stress perfusion scan, stress Sestamibi)

A diagnostic study, which uses a small amount of radioactive tracer, injected into the body, and a special camera, which detects the radiation, released by the substance to produce a computer image of the heart. Combined with exercise, the study can help determine if there is adequate blood flow to the heart at rest, as compared with activity.

+ Silent Ischemia

Inadequate supply of oxygen-rich blood to the heart that does not cause symptoms such as chest pain.

+ Sinoatrial Node (SA or sinus node)

A specialized cluster of cells in the heart that initiates the heartbeat. Known as the heart’s natural pacemaker.

+ Sodium

A mineral found in most of the foods we eat. The largest source of dietary sodium comes from sodium chloride or table salt. Intake of sodium tends to increase the retention of water.

+ Sphygmomanometer

A device for measuring blood pressure.

+ Stenosis

Narrowing or restriction of a blood vessel or valve that reduces blood flow.

+ Stent

A small stainless steel mesh tube, inserted after angioplasty, that acts as a scaffold to provide support inside the coronary artery.

+ Sternum (breastbone)

Bone in chest separated during open heart surgery.

+ Stress Test

See Exercise Stress Test.

+ Stroke

A sudden loss of brain function due to decreased blood flow to an area of the brain.

+ Stunned Myocardium

If blood flow is returned to an area of heart muscle after a period of ischemia (lack of blood supply), the heart muscle may not pump normally for a period of days following the event. This is called “stunned” heart muscle or myocardium.

+ Subvalvular Aortic Stenosis

A narrowing of the flow of blood below the aortic valve in the left ventricle. It is usually caused by a membrane or thickening in the muscle in this area.

+ Syncope


+ Systole

The portion of the cardiac cycle in which the heart muscle contracts, forcing the blood into the main blood vessels.

+ Systolic Pressure

The pressure of the blood in the arteries when the heart pumps. It is the higher of two blood pressure measurements (for example, 120/80, where 120 is the systolic pressure).

+ Tachycardia

Rapid heartbeat. A heart rate above 100 beats per minute.

+ Thallium Exercise Stress Test (Stress thallium test, Perfusion scan)

A type of nuclear scanning technique that uses the radioactive substance thallium. A thallium stress test combines nuclear scanning with exercise on a treadmill or stationary bicycle to assess heart function and determine if there is adequate blood flow to the myocardium.

+ Thrombolytic Medication (clot-buster drug)

Medication used to dissolve any clots that may be blocking blood flow in arteries and veins.

+ Thrombus

A blood clot.

+ Total Cholesterol

The total amount of cholesterol in the blood.

+ Transesophogeal Echocardiogram (TEE)

An invasive imaging procedure that creates a picture of the heart’s movement, valves and chambers using high frequency sound waves that come from a small transducer passed down your throat. TEE provides clear images of the heart’s movement because the transducer is close to the heart and limits interference from air in the lungs. Echo is often combined with Doppler ultrasound and color Doppler to evaluate blood flow across the heart’s valves.

+ Transient Ischemic Attack (TIA)

A stroke-like event lasting minutes, or hours, that occurs when the brain is deprived of oxygen-rich blood but in which the effects wear off completely after resumption of blood-flow.

+ Trans-Myocardial Revascularization (TMR)

A procedure used in people with severe heart disease who are not candidates for bypass surgery. In this procedure, an incision is made in the chest. The heart is exposed and small holes are drilled through the wall of the heart with a laser.

+ Transtelephonic Monitor

A small monitor is attached to electrode leads (usually on your finger or wrist). Your heart’s rhythm is transmitted over the phone line with the aid of this device to your doctor’s office.

+ Tricuspid Valve

The tricuspid valve is the valve that separates the right atrium from the right ventricle and prevents blood from flowing back into the right atrium during contraction of the ventricle.

+ Triglyceride

A fat found in the blood. Most fat found in the diet and body is in the form of triglycerides.

+ Unstable Angina

This type of angina is considered an acute coronary syndrome. It may be a new symptom or a change from stable angina. It may come more often, occur at rest, or feel more severe. Although this angina can be relieved with oral medications, it is unstable and may progress to a heart attack. Usually medical treatment or a procedure is required in the near future.

+ Valve

Structures that maintain the proper direction of blood flow. There are four valves in the heart: the tricuspid and the mitral valve, which lie between the atria and ventricles and the pulmonic and aortic valves which lie between the ventricles and the blood vessels leaving the heart.

+ Valvuloplasty

A procedure to improve valve function. Balloon valvuloplasty is when a balloon is used to at the time of cardiac catheterization to increase the area of a narrowed valve.

+ Variant Angina

A type of angina that occurs at rest most often due to coronary spasm.

+ Vasodilator

A type of medication that relaxes and dilates the blood vessels, allowing increased blood flow.

+ Veins

Blood vessels that carry blood toward the heart.

+ Ventricles

The lower, pumping chambers of the heart. The heart has two ventricles – the right and left ventricle.

+ Ventricular Fibrillation

An erratic, disorganized firing of impulses from the ventricles. The ventricles quiver and are unable to contract or pump blood to the body. This is a medical emergency that must be treated with cardiopulmonary resuscitation (CPR) and defibrillation as soon as possible.

+ Ventricular Rupture

In people who suffer a significant heart attack, it is sometimes the case that the area of the muscle wall of the heart that is affected can become so weakened that it ruptures and leaks blood from the inner chamber of the heart.

+ Ventricular Septal Defect

The right and left ventricles lie next to each other in the heart. The septum is the membranous wall that separates them. A ventricular septal defect is a hole in the septum.

+ Ventricular Tachycardia

A rapid life-threatening rhythm originating from the lower chambers of the heart. The rapid rate prevents the heart from filling adequately with blood, and less blood is able to pump through the body.

+ Wolff Parkinson White Syndrome (WPW)

WPW is a form of supraventricular tachycardia (fast heart rate originating above the ventricles). People with WPW have more than one electrical conduction pathway in their hearts (accessory pathways.) These electrical impulses set up a short circuit causing the heart to beat rapidly and conduct impulses in both directions. The impulses travel through the extra pathway (short cut) as well as the normal AV-His-Purkinje system. The impulses can travel around the heart very quickly, in a circular pattern, causing the heart to beat unusually fast. This is called re-entry tachycardia.

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Reviewed by the doctors at The Cleveland Clinic Heart Center.
Glossary Credits: WebMD

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