Nebraska Heart Institute

Medical Glossary

AICD (Automatic Implantable Cardioverter Defibrillator): a special device used to detect and treat abnormally fast heart rhythms. The AICD system usually consists of an implanted pulse generator and one or more leads. The system is adjusted using an external programming device.

Angina: Commonly called chest pain, heart pain or angina pectoris. Usually, it is felt as a discomfort or pressure in the chest, arms, jaw or back (between the shoulder blades). Some people experience shortness of breath, fatigue, weakness or stomach discomfort (indigestion or "heartburn"). Angina is a result of an inadequate supply of oxygenated blood to the heart muscle due to blockages in the coronary arteries (and/or bypass grafts).

Arrhythmia: any rhythm of the heart that is faster or slower than the average heart rate and regularity for most people.

Atherectomy: A procedure that removes a coronary blockage from the coronary vessel. By removing plaque from the artery, the blood vessel is opened for better blood flow. This procedure is performed by passing a special device into the coronary blockage.

Atria: the upper chambers of the heart, specifically the right atrium and left atrium. The atria collect blood as it comes into the heart and fill the lower chambers (ventricles) with blood.

Blood Pressure: is the force applied against the walls of the arteries as the heart pumps blood through the body. This is measured in millimeters of mercury (mm Hg). Blood pressure changes constantly due to activity, temperature, diet, emotional stress, posture, physical state, and medication/drugs.

Bradycardia: a slow heartbeat, typically less than 60 beats per minute (bpm). It may be caused by the sinoatrial (SA) node not working properly or by a condition called heart block.

Cardiac Arrest: the heart beats very fast or stops completely so that no blood is being pumped out to the body.

Cardiac Catheterization: Also referred to by a variety of terms, such as Coronary Angiogram, Heart Catheterization, Cardiac Cath and Heart Cath. This is a diagnostic procedure performed by a cardiologist to evaluate the status of the coronary arteries and bypass grafts. During the Cardiac Catheterization, a small plastic tube (catheter) is guided to each of the coronary arteries and bypass grafts (if you have them). An injection of X-Ray contrast material is delivered into the coronary vessel to outline the arteries and blockages while X-Ray pictures are taken.

Cardioversion: the stopping of a fast heart rate by an electrical impulse that is delivered at the same time as the heartbeat. It uses low to moderate energy to restore the heart's normal rhythm.

Contraction: the rhythmic squeezing of the heart muscle that causes blood to be pumped out of the heart chambers and into the body. This contraction produces a heartbeat.

Coronary Arteries: Blood vessels that carry oxygenated blood to the heart muscle. If these vessels become blocked, the heart muscle will not receive an adequate supply of oxygen and nutrients.

Coronary Artery Disease (CAD): Also called Heart Disease or Atherosclerosis. This term is used to describe the gradual narrowing of the coronary arteries from the accumulation of plaque in the arterial wall. This leads to a reduction of blood flow to the heart muscle and may result in symptoms (angina).

Not all patients experience symptoms of CAD. However, if left untreated, CAD eventually may cause a complete interruption of coronary blood flow, resulting in a heart attack or Myocardial Infarction.

Defibrillation: the stopping of a fast heart rate by delivering a high-energy electrical shock to restore the heart's normal rhythm.

Defibrillator: an internal or external device that can deliver an electric shock to stop extremely rapid and irregular heartbeats and return the heart to a normal rhythm.

EGG/EKG (electrocardiogram): a test to show your heart rhythm printed out on paper. The test shows how electrical impulses travel through your heart. Your doctor can tell what kind of rhythm you have by looking at the printed pattern of your heartbeat.

Electrocautery: the use of electrical currents to stop bleeding during surgery.

Electrogram (EGM): a picture of the electrical activity of the heart as sensed from within the heart. This is different from an ECG, which is a picture of your heart's electrical activity sensed from the surface of your skin.

Electromagnetic Field: invisible lines of force that are the result of the use of electricity, such as anything plugged into an outlet or operated by a battery.

Electromagnetic Interference (EMI): produced by an electromagnetic field. If it is strong enough, it may interfere with the operation of an AICD system; this happens only on very rare occasions.

Electrophysiology (EP) Test or Study: a test where wires are inserted into your heart to identify and measure the type of electrical signals in your heart. The test results can help your doctor recognize your abnormal heart rhythm, determine how well medications work, and decide what treatment is best. The test also can be used to see how well your AICD system operates during your abnormal heart rhythm.

Endocardial: the inside surface of the heart. Endocardial leads are inserted into the heart through the veins.

Epicardial: the outside surface of the heart. Epicardial leads are placed on the heart during open-chest surgery.

Exercise Stress Test: A simple screening test whereby the patient is asked to walk on a treadmill machine or ride a bicycle to increase the number of times the heart pumps each minute. If the patient has CAD, the continuous ECG monitor may tell the doctor that coronary artery blockages are present. However, this test will not give the exact location of the blockages. A Cardiac Catheterization is performed later to find the location and extent of suspected coronary blockages and to confirm results of an Exercise Stress Test.

Heart Attack: also called myocardial infarction (MI), this occurs when an artery that feeds the heart becomes blocked. As a result, blood does not get to some parts of the heart and some of the heart tissue dies. The symptoms may include nausea, shortness of breath and/or pain in the chest, arm or neck.

Heart Rhythm: another word for a heartbeat. You may hear your doctor refer to your rhythm as being normal or irregular, meaning there is an abnormality. A normal heart rate typically ranges from 60 to 100 beats per minute at rest.

Hypertension (high blood pressure): an elevated blood pressure level that is continual or intermittent. If left untreated it increases the risk for heart failure, heart attack, stroke, and kidney failure.
Normal blood pressure: 120 mm Hg/80 mm Hg.
Borderline High: 145-159 mm Hg/ 90-104 mm Hg.
High: over 160 mm Hg/100 mm Hg.

Implanted: placed inside the body. The AICD system is an implanted system.

Lead: an insulated wire that carries the heart signal to the pulse generator and energy from the pulse generator to the heart. The leads are attached to the surface of the heart or passed into your heart through the veins.

Myocardial Infarction (Heart Attack): A life-threatening condition caused by complete interruption of blood flow through a coronary artery or bypass graft. This condition requires immediate medical attention. Symptoms include discomfort (pain) or pressure in the chest, arms, jaw or back (usually between the shoulder blades). Other symptoms include shortness of breath, fatigue, weakness or stomach discomfort (indigestion or "heartburn"). If any of these symptoms are felt for more than five (5) minutes and are not relieved by rest (and/or your heart medications), seek medical attention immediately.

Pectoral: the area near the breast or upper chest.

Plaque: Also called "atheroma," plaque is a localized area of arterial or bypass graft narrowing (atherosclerosis). Plaque is composed of cholesterol (and other materials) and can be accompanied by thrombus (blood clots).

Programmer: microcomputer-based equipment used to communicate with the pulse generator. It provides information during testing and follow-up exams. The doctor uses the programmer to adjust the pulse generator so that it senses and treats your arrhythmias. The programmer can, for example, help your doctor discover when the pulse generator needs to be replaced.

PTCA: Percutaneous Transluminal Coronary Angioplasty, commonly called balloon angioplasty. This procedure is performed to improve coronary blood flow that is slowed by blockages. To perform this procedure, a catheter with a balloon on its tip is passed into the coronary blockage. The balloon is inflated, cracking and splitting the plaque and stretching the wall of the coronary vessel to allow more blood flow to the heart muscle.

Pulse Generator: the part of the AICD system that contains the electronics and the battery; it is implanted under the skin in the abdominal or pectoral area.

Sinoatrial (SA) node: the small area in the upper right chamber of your heart that normally generates an electrical impulse. This impulse runs through the heart and causes the heart to beat.

Sternotomy: a lengthwise incision through the breastbone (sternum) that may be made when heart surgery is performed.

Subcutaneous (so): beneath the skin.

Sudden Cardiac Death (SCD): a death due to electrical problems in the heart. (It is different from a heart attack, which is heart muscle damage from a blockage rather than an electrical problem.) Sudden cardiac death is usually caused by ventricular tachycardia or fibrillation. An AICD system, however, greatly reduces the risk of sudden cardiac death.

Thoracotomy: an incision into the chest that may be made when heart or lung surgery is performed.

Transvenous: passed into the heart through a vein. See endocardial.

Ventricle: one of the two lower chambers of the heart. The right ventricle sends blood to the lungs, and the left ventricle passes blood carrying oxygen to the rest of the body.

Ventricular Fibrillation (VF): a very fast, irregular heart rate caused by abnormal impulses starting from several areas of the ventricle. The heart beats so fast that it is unable to pump any blood to the body. A heart in fibrillation may beat over 300 times a minute. A person in fibrillation passes out and needs immediate medical attention in order to live.

Ventricular Tachycardia (VT): a fast heartbeat caused by abnormal impulses coming from a single area of the ventricle. The rapid rate of 120-250 beats per minute may produce dizziness, weakness, blind spots and, eventually, unconsciousness.