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waveforms
waveforms, intervals, segments
Term | Definition |
---|---|
P wave | the first wave in the cardiac cycle representing atria depolarization. |
Depolarization | asystole; contraction |
QRS wave | also known as QRS complex; the second wave in the cardiac cycle representing ventricular depolarization (atrial repolarization is not visible but occurs during this phase |
repolarization | systole; relaxation |
T wave | the third wave in the cardiac cycle representing ventricular repolarization |
bundle of His | a collection of fibers that conduct the electrical impulses from the AV node to the ventricular septum |
Purkinje fibers | the fingerlike projections that spread through the ventricular muscle and initiate ventricular contraction |
P-R interval | the length of time from the beginning of atrial depolarization to the beginning of ventricular depolarization. starts at the beginning of the P wave and ends at the beginning of the Q wave. |
U wave | not always visible but represents a repolarization of the bundle of His and Purkinje fibers. |
QT interval | starts at the beginning of the Q wave and ends at the end of the T wave. represents the time it takes form the beginning of ventricular depolarization to the end of ventricular repolarization |
ST segment | starts at the end of S wave and ends at the beginning of the T wave. it represents the time from the end of ventricular depolarization to the beginning of ventricular repolarization |
normal P wave | should be positively deflected. |
positive deflection | an upward curvature of waves in an EKG tracing |
negative deflection | a downward curvature of waves in an EKG tracing. |
atrioventricular (AV) node | the secondary pacemaker located at the junction of the atria and ventricles. |
premature ventricular contractions (PVCs) | one of the most common abnormal waves associated with the ventricles |