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ECG Key Terms
alternating current (AC) interference
electrical interference that appears as small, uniform spikes on ECG tracing.
device on the electrocardiograph that magnifies or enlarges the heart's electrical impulses so they can be recorded.
abnormal heart rate, rhythm, and conduction system; also called dysrhythmia.
unwanted changes in an ECG tracing caused by movement, machine malfunction, or other factors.
atrioventricular (AV) node
knot of specialized cells in the lower portion of the right atrium that produces the heart's electrical impulses.
leads that measure cardiac activity from one electrode on the body at a time; recordings are augmented (made larger) so they can be read.
line that separates the various cardiac waves; representative of the space between heartbeats while the heart is "resting"; also called isoelectric line.
standard limb leads.
bundle of branches
branches of cardiac fibers that receive electrical impulses from the bundle of His.
bundle of His
small band of atypical cardiac muscle fibers that receive electrical impulses from the AV node.
one heartbeat; one contraction/relaxation phase of the heart.
graphic picture of the heart's electrical activity.
machine that records the electrical activity of the heart.
device that detects and converts the amplified electrical signal into a tracing on the ECG machine.
ECG pattern that shows the length of a wave with a segment.
poor blood supply to body tissue causing a lack of oxygen to that tissue.
(MI) heart attack; death of heart tissue caused by blockage of the heart's blood vessels.
normal sinus rhythm (NSR)
rhythm measurement that start at the SA node, occurs within an established time frame, and follows an expected, established pattern.
paroxysmal atrial tachycardia (PAT)
sudden onset and ending of atrial tachycardia, 150 to 250 beats per minute.
time interval between atrial contraction and the beginning of ventricular contraction.
premature atrial contraction (PAC)
condition in which an electrical impulse in the atria starts before the next expected heartbeat.
premature ventricular contraction (PVC)
condition in which the ventricles receive an impulse prematurely and contract early.
cardiac fibers that receive impulses from the bundle branches and take them throughout the heart muscle.
ECG pattern that shows when the impulse moves through the ventricles and reaches the Purkinje fibers, depicting contraction of both ventricles.
rest phase of the ECG cycle.
process of ensuring that an ECG taken on one machine will compare to a tracing taken on another machine.
heated device that records the heart's activity on heat-sensitive graph paper.
recording of the ECG cycle.
normal, small upward curve that occasionally follows a complete ECG cycle after the PQRST; has unknown indication.
ventricular fibrillation (V fib)
life-threatening condition of ventricular twitching that causes ineffective pumping action, stopping blood circulation.
shift on the ECG tracing from the baseline or center of the paper.
ECG pattern that represents specific electrical heart activity.