Master ECG / EKG Components for Nursing

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.