Glossary of Medical and Electrophysiological TermsA B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Ablation Catheter ablation is the therapeutic destruction of a small part of heart muscle shown at an electrophysiologic study to be responsible for an arrhythmia.
Amiodarone (Cordarone) is an antiarrhythmic agent (class III) widely used for acute (intravenous) and chronic (tablets) treatment of both ventricular and supraventricular arrhythmias. Unlike antiarrhythmic agents with local anesthetic effects (Class I agents), it has little propensity to produce rhythm disturbances (see proarrhythmia).
Angina Pectoris (Latin = suffocation chest) Chest pain or feeling of tightness due to lack of blood supply to the heart muscle because of obstruction or constriction of the coronary arteries (CAD).
Angioplasty (Greek = vessel form) Dilation of an artery obstructed by plaque.
Antiarrhythmic agents Medications for the prevention or termination of arrhythmias. They are categorized into four groups according to their presumptive mechanism of action:
Type I predominantly inhibit sodium ion channels and act as local anesthetics. Class I drugs are effective agents, but may depress heart performance and induce arrhythmias under special circumstances (proarrhythmia). Examples: quinidine, lidocaine, procainamide (Pronestyl), and disopyramide (Norpace).
Type II is known as beta receptor blockers (beta adrenergic receptor blockers). Adrenalin ( = epineprine) acts partly through these receptors. These drugs may reduce mortality in patients recovering from a heart attack or suffering from heart failure. Examples: propranolol (Inderal), metoprolol (Lopressor), atenolol (Tenormin), nadolol (Corgard), carvedilol (Coreg).
Type III inhibits potassium ion channels and prolongs recovery after electric activation of cardiac cells. Currently the drugs of choice for the prevention of serious (ventricular) arrhythmias; also useful to prevent or terminate supraventricular arrhythmias. Examples: amiodarone (Cordarone), sotalol (Betapace).
Type IV inhibits calcium channels, which influence impulse conduction at the level of the AV node. Because these drugs relax (widen) small blood vessels, they are useful for the treatment of high blood pressure. Examples: verapamil, ditiazem.
Aorta The main artery of the body and the only one directly connected to the heart. It runs along the spine and distributes nutrient and oxygen rich blood to all organs and body parts. See Normal Heart Structure & Function
Arrhythmia An abnormal heart rhythm. The rate may be irregular, slow, or rapid.
Arrhythmogenic right ventricular dysplasia (ARVD) A rare condition that produces ventricular tachycardia. In this disease ventricular muscle is replaced by fatty and fibrous tissue for unknown reasons. It is emerging as a cause of sudden cardiac death (SCD) in young otherwise healthy adults.
Atherosclerosis (hardening of the arteries) (Greek gruel-hardening) "Hardening of the Arteries" A disease of the large arteries in which deposits of plaques are formed on the inner walls of the arteries and obstruct the blood flow. Clogged up arteries are the major cause of heart attacks and strokes.
Atria (singular = atrium) The two receiving chambers of the heart. The left atrium receives oxygenated blood from the lungs and delivers it to the left ventricle. The right atrium passes oxygen-depleted blood from the veins to the right ventricle. See Normal Heart Structure & Function
Atrial fibrillation (AF) An atrial arrhythmia with highly irregular electric and mechanical activity of the atrial chambers. The lost normal pacemaker function of the right atrium results in an irregular, often rapid, heartbeat. In AF (Latin: fibrilla = small muscle) individual areas in the atria contract independently, at different times, producing quivering but no purposeful contraction.
Atrial flutter A supraventricular tachycardia with a characteristic electrocardiographic appearance. It frequently coexists with atrial fibrillation and is usually associated with structural heart disease.
Atrial tachycardia A rapid rhythm driven by pacemaker activity in atrial sites other than the SA node (the natural pacemaker).
Atrioventricular (AV) node A collection of cells that establish an electrical connection between the otherwise electrically isolated atria and ventricles. May act as a secondary pacemaker. See Normal Heart Structure & Function
Atrioventricular nodal reentrant tachycardia (AVRT) A supraventricular tachycardia caused by dual conduction pathways within the AV node which have different speeds of transmission.
AV block See Heart block
Bradycardia (brady = slow) A slow heart rate of less than 60 beats/per minute.
Brugada syndrome An inherited electrical disease of the heart.
Cardiac arrest Any cessation of useful contraction of the hearts main pumping chamber. See Sudden Cardiac Death (SCD)
Cardiac catherization A diagnostic test of the heart to detect coronary artery disease and to see how well the heart muscle contracts and the valves function.
Cardiac tamponade Effusion of fluid in the pericardium (sac enclosing the heart) compresses the heart preventing normal filling.
Cardiomyopathy (cardio = heart; myo = muscle; pathy = disease) diffuse heart muscle disease:
Dilated cardiomyopathy an increase in chamber size. (filling volume of the chamber).
Hypertrophic cardiomyopathy (HCM) thickening of the walls of the heart chambers.
Idiopathic CMP heart muscle disease of unknown cause.
Cardioversion Delivery of a shock to the heart to interrupt arrhythmias. Paddles on the chest or electrodes placed directly on the heart are used. So called chemical cardioversion is intravenous administration of medications to terminate arrhythmias.
Congenital heart disease A heart defect present at birth.
Congestive heart failure (CHF) See Heart failure
Continuous loop recorder An electrocardiographic monitor worn for up to a month that stores limited periods of continuously recorded ECG.
Coronary arteries (Corona = crown) The arteries that encircle and supply nourishing blood flow to the heart muscle.
Coronary spasm is abnormal sustained constriction of a major coronary producing symptoms of ischemia.
Coronary artery disease (CAD) The presence of fat, calcium, and blood clot deposits in the coronary arteries.
Defibrillation The delivery of a shock to terminate atrial or ventricular fibrillation and restore normal heart rhythm. Defibrillators use paddles on the chest or electrodes placed directly on the heart.
Depolarization Resting cardiac cells generate a voltage or "polarization" across their surface membrane. When cells are electrically stimulated, the resting polarization is reversed or "depolarization occurs due to a movement of ions across the membrane.
Disopyramide (Norpace) A medication introduced in 1969 to treat supraventricular arrhythmias. See Antiarrhythmic Agent Class I.
ECG (electrocardiogram or EKG) A record of the electric activity of the heart from the bodys surface.
Echocardiography A noninvasive test using ultrasound to visualize the structure of the heart, the contractile function of the chambers (ejection fraction) and information on blood flow velocity (Doppler flow analysis).
Electromagnetic interference (EMI) Impaired function of a pacemaker or ICD under the influence of electric and magnetic fields emitted by Magnetic Resonance Imaging (MRI), power plants, transmitter antennas, amusement parks, or nearby equipment such as, arc welders, CB radios, cellular phones, etc.
Electrophysiologist Cardiac electrophysiologist are cardiologists with expertise in the diagnosis and treatment of the hearts electrical system.
Electrophysiology (EP) study The EP study, a type of heart catheterization, is used to investigate and diagnose a broad range of arrhythmias. Electrical recordings are gathered both from the inside of the heart the body surface.
Epinephrine A vital hormone secreted by the adrenal glands. It plays an important role in cardiovascular and neural regulation. It is produced synthetically for use as a stimulant.
Extrasystoles Extra beats, usually occurring earlier than expected in normal rhythm, triggered by impulses originating from an abnormal site. Premature contractions are common and usually require no treatment. However for patients with underlying heart disease they can be markers of a life threatening arrhythmia. Premature contractions PAC and PVC originate in the atria and ventricles respectively and Premature Junctional (AV nodal) originates in the vicinity of the AV node junction.
Flecainide (Tambocor) A medication introduced many years ago to treat supraventricular arrhythmias. See Antiarrhythmic Agent Class I
Heart block A more appropriate term is atrioventricular (AV) block. Delay or failure of electrical impulse conduction through the AV conduction system.
Heart failure (HF) HF is a condition where the heart fails in its duties of circulating blood through the lungs and back out to the tissues. Congestive heart failure refers to a heart failure condition in which the body has accumulated extra fluid so that the lungs are congested.
His bundle The topmost part of the hearts wiring system between the AV node and the ventricles. The His bundle penetrates the electrically insulating fibrous layer between the atria and ventricles. See Normal Heart Structure & Function
His-Purkinje system A network of nerve-like fibers that carry the electrical signal from the His bundle to the heart muscle itself. See Normal Heart Structure & Function
Hypokalemia Low potassium concentration in the blood. Low potassium concentrations may invite arrhythmias. Certain diuretics may increase loss of potassium and produce hypokalemia.
Holter monitor A 24-hour ECG monitor worn by the patient.
Ibutilide (Corvert) An antiarrhythmic drug used for atrial fibrillation and flutter that works by prolonging the recovery of the heart muscle after electrical stimulation. See Antiarrhythmic Agent Class III
ICD (Implantable Cardioverter-Defibrillator) A device implanted under the skin in the upper chest or abdominal that delivers a shock to terminate ventricular tachycardia or fibrillation and restores normal rhythm.
Ischemia (ischemic = with held) is reduced nutrient blood flow to organs or tissue resulting in reversible or irreversible damage to tissue.
Ischemic Heart Disease is disease of heart muscle associated with ischemia. See coronary artery disease (CAD)
Left ventricular ejection fraction (LVEF) is the amount of blood ejected during a single contraction of the LV, expressed as a fraction of the amount of blood the LV contains at the onset of contraction. It measures the completeness of active ventricular emptying, an index of functional adequacy. Normal LVEF at rest is about 2/3 or 66%. See Normal Heart Structure & Function or Heart Failure
Lidocaine A drug administered intravenously for acute management of ventricular arrhythmias or for local anesthesia. See Antiarrhythmic Agent Class I
Long QT syndrome An inherited electrical disease of the heart.
Mexiletine (Mexitil) A medication introduced in 1973 to treat ventricular arrhythmias. See Antiarrhythmic Agent Class I
Mitral valve The valve between the left atrium and the left ventricle functions like a one way door to keep blood flowing in one direction as it enters the left ventricle from the left atrium.
Moricizine A medication to treat ventricular arrhythmias. See Antiarrhythmic Agent Class I
Myocardial infarction (MI) A heart attack. See Coronary Artery Disease
Myocardial perfusion imaging Mapping of nutrient blood flow through the heart muscle by using radioactive markers detected by a special camera.
Myocarditis Heart muscle inflammation, due to invading infectious agents (bacteria, virus, fungi, etc.) or immune processes.
PAC Premature Atrial Contractions See Extrasystoles
Pacing Delivery of electrical stimulation to the heart muscle to produce a heart beat.See Electrophysiologic (EP) study
Pacemaker (Artificial) An electrical device which delivers electrical impulses to produce a heart beat of desired frequency (fixed frequency). Modern pacemakers "kick in" on demand only when heart rate falls below a critical (chosen) value and may deliver impulses at rates adapted to physical activity (rate adapted). Implantable pacemakers are the mainstay of treating slow heart rhythms.
Pacemaker cells cardiac cells whose electrical oscillatory activity (clock like function) release electrical impulses eliciting rhythmic cardiac contraction. See Normal Heart Structure & Function
Pericarditis Inflammation of the pericardium. See heart failure
Pericardium a bag-like structure surrounding the heart and containing fluid to ease cardiac movement.
Proarrhythmia Creation of a new arrhythmia by drugs.
Procainamide A medication introduced in 1950 to treat supraventricular and ventricular arrhythmias. See Antiarrhythmic Agent Class I
Pulmonary artery The artery originating from the hearts right ventricle that carries oxygen-depleted blood to the lungs.
Pulmonary valve The valve between the right ventricle and the pulmonary artery.
PVC Premature Ventricular Contraction - See Extrasystoles
P Wave part of the ECG recording reflecting depolarization of both atria.
Q Wave First wave of the ECG recording reflecting ventricular activation.
QRS Complex part of the ECG recording reflecting ventricular depolarization.
QT interval period of the ECG recording from the onset of the Q wave to the T wave.
Quinidine An antiarrhythmic drug introduced in 1918 used for treatment of ventricular and supraventricular and arrhythmias. See Antiarrhythmic Agent Class I
Repolarization Active restoration of resting polarization.
Reentrant circuit See Junctional Tachycardias
Sick sinus syndrome A disease of the atria affecting both impulse generation and conduction. It is manifested by both rapid and slow rhythms (tachy-brady syndrome) and is usually associated with aging.
Sinoatrial (SA) node The hearts natural pacemaker in which the electrical impulse to generate a heartbeat originates. See Normal Heart Structure & Function
Sinus rhythm - Normal sinus rhythm (NRS) A normal heart rhythm of 60-100 beats per/min at rest originating from the sinoatrial node.
Sinus tachycardia A normal heart rate greater than 100 beats/min. It occurs as a desirable response to exertion, pregnancy, and emotion. It may also occur with, illness, circulatory problems, or drug use.
Sotalol (Betapace) A medication having great clinical utility for the control for a wide spectrum of arrhythmias. It dampens down electrical activity by combining the effects of inhibiting potassium ion channels with beta blocker effects. See Antiarrhythmic Agent Class III
ST segment the segment of the ECG recording connecting the end of the QRS complex with the beginning of the T wave.
Sudden cardiac death (SCD) Generally SCD is defined as an unexplained (non-traumatic) death that occurs suddenly and unexpectedly within one hour of onset of symptoms. Death is usually due to cardiac arrhythmias ventricular tachycardia/fibrillation.
Supraventricular tachycardia (SVT) Arrhythmias caused by electrical events originating in the atria, i.e. above the ventricles.
Syncope A brief transient loss of consciousness due to decrease in blood flow to the brain.
T Wave ventricular repolarization wave inscribed on the ECG.
Tachycardia (tachy = fast) a rapid heart rhythm.See Irregular Rhythms
Tilt table test a test that involves placing the patient on a special table and standing him or her upright at 60 to 70 degrees for 30 to 45 minutes.
Torsade de pointes (Twisting of the points) A unique form of ventricular tachycardia that can be congenital in origin or can result from antiarrhythmic or psychotropic drug therapy, hypocalcemia, or acute myocardial infarction.
Transtelephonic event recorder A miniaturized computer chip operated unit that stores brief ECG recordings when patients experience symptoms.
Tricuspid valve The valve between the right atrium and the right ventricle that functions like a one way door to keep blood flowing in one direction as it enters the right ventricle from the right atria. See Normal Heart Structure & Function
Ventricles The two main ejecting chambers of the heart. The left ventricle pumps oxygenated blood through the bodys arterial system. The right ventricle pumps blood into the lungs to be oxygenated.
Ventricular fibrillation (VF) A rapid, disorganized, and chaotic contraction of ventricular muscle accompanied by loss of effective pumping of blood. It results in loss of consciousness and death if is not terminated immediately by delivery of shock with a defibrillator.
Vasodilators are drugs that widen (dilate) blood vessels. They unload the heart because it requires less effort to pump a given amount of blood per minute through a system of wide vessels compared with narrow ones.
Ventricular tachycardia (VT) A very rapid heart rhythm arising within the ventricles.
Warfarin (Coumadin) An anticoagulant drug used since 1941 to prevent blood clots.
Wolff-Parkinson-White syndrome A syndrome with abnormal ECG and where aberrant conducting pathways allow inappropriate transmission of signals from the atria to the ventricles or back to the atria from the ventricles.