Electrocardiography, Dr. D. Penney
Table 9. ECG TERMINOLOGY - WAVES
P Wave - precedes the QRS complex; initial part due to RA depolarization, latter part due to LA depolarization.
QRS Complex (40 - 80 msec.):
- - Q Wave - first downward deflection of the QRS complex; may include activation of septum, initial activation of ventricles, depending upon lead.
- - R Wave - first upward deflection of the QRS complex; usually due to ventricular depolarization; usually the highest amplitude wave, except for an electronic pacemaker.
- - S Wave - second downward deflection of the QRS complex, after R wave; last part of ventricles to get activated (base of ventricle).
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