The P wave represents electrical conduction between the atria. The P wave is normally upright and lasts between 0.06 to 0.12 seconds. There should be one P wave for every QRS complex. An abnormal P wave may be caused by a disturbance of conduction within atria.
Atrial depolarization involves the contraction of the atria and is measured by the P wave.
The QRS complex measures the duration for depolarization of both ventricles. A normal QRS complex is less than 0.12 seconds. Disturbances in conduction in bundle branches or the ventricles disrupt a normal QRS complex.
Ventricular depolarization is measured by the QRS complex. Systole is caused by ventricular conduction.
The T wave represents repolarization of the ventricles. A normal T wave is upright and lasts 0.16 seconds. A tall, peaked, or inverted T wave may be caused by electrolyte imbalances, ischemia, or myocardial infarction.
Ventricular repolarization is measured by the T wave.
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