Ejection Fraction: The percentage of blood filling the left ventricle during each heartbeat that flows out of the ventricle into the body’s circulatory system. This reading is a direct measure of the “pumping” capability of the heart. Damaged/diseased hearts may have an ejection fraction below 50%.
Electrocardiogram (ECG/EKG): A method of recording the electrical impulses given off by the heart as it beats. This may be done while resting or exercising.
Electrocautery: The use of electrical currents to stop bleeding during surgery.
Electrode: Transmits or receives electrical impulses from one point to another.
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 strong enough, it may interfere with the operation of an AICD system. This happens only on very rare occasions.
Electrophysiology (EP) Test or Study: An observation and measurement of the electrical impulses running through the heart as it beats. This test can help a doctor to recognize abnormal heart rhythms, to determine the origin of arrhythmias and to determine how well medicines are working. A doctor may also use the test to observe the implantable defibrillator to see how well it functions during an abnormal heart rhythm.
Endocardial: The inside surface of the heart. Endocardial leads are inserted into the heart through the veins.
Endocardial Lead: A long, thin insulated wire that runs from a pulse generator through a vein into the heart. The lead transmits signals from the heart to the pulse generator and transmits therapy from the pulse generator to the heart.
Epicardial: The outside surface of the heart. Epicardial leads are placed on the heart during open-chest surgery.
Echocardiography: A method of studying the heart’s structure and function by analyzing sound waves bounced off the heart and recorded by an electronic sensor placed on the chest. A computer processes the information to produce a one-, two- or three-dimensional moving picture that shows how the heart and heart valves are functioning.
Edema: Swelling caused by fluid accumulation in body tissues.
Ejection Fraction: A measurement of blood that is pumped out of a filled ventricle. The normal rate is 50 percent or more.
Electrocardiogram: A test in which several electronic sensors are placed on the body to monitor electrical activity associated with the heartbeat.
Electroencephalogram: A test that can detect and record the brain’s electrical activity. The test is done by pasting metal disks, called electrodes, to the scalp.
Electrophysiological Study: A test that uses cardiac catheterization to study patients who have arrhythmias (abnormal heartbeats). An electrical current stimulates the heart in an effort to provoke an arrhythmia, which is immediately treated with medicine. EPS is used primarily to identify the origin of arrhythmias and to test the effectiveness of medicines used to treat abnormal heart rhythms.
Embolus: Also called embolism; a blood clot that forms in a blood vessel in one part of the body and travels to another part.
Endarterectomy: Surgical removal of plaque deposits or blood clots in an artery.
Endocardium: The smooth membrane covering the inside of the heart. The innermost lining of the heart.
Endothelium: The smooth inner lining of many body structures, including the heart (endocardium) and blood vessels.
Endocarditis: A bacterial infection of the heart’s inner lining (endothelium).
Enlarged Heart: A state in which the heart is larger than normal due to heredity, long-term heavy exercise, or diseases and disorders such as obesity, high blood pressure, and coronary artery disease.
Enzyme: A complex chemical capable of speeding up specific biochemical processes in the body.
Epicardium: The thin membrane covering the outside surface of the heart muscle.
Estrogen: A female hormone produced by the ovaries that may protect premenopausal women against heart disease. Estrogen production stops after menopause.
Estrogen Replacement Therapy: Hormones that some women may take to offset the effects of menopause.
Exercise Stress Test: A common test for diagnosing coronary artery disease, especially in patients who have symptoms of heart disease. The test helps doctors assess blood flow through coronary arteries in response to exercise, usually walking, at varied speeds and for various lengths of time on a treadmill. A stress test may include use of electrocardiography, echocardiography, and injected radioactive substances.