A PVC is a single ectopic beat generated by an impulse from an irritable focus in the ventricles. It is not a rhythm, but it does disrupt the regularity of the underlying rhythm.

There is no P wave associated with a PVC complex because there is no corresponding atrial depolarization. The QRS complex is wide (≥ 120 milliseconds). 

The morphology of the T wave in a PVC is a peculiar feature that makes the PVC easy to spot on an ECG strip. The T wave has a positive deflection and appears just after the negative deflection of the QRS complex. (see Figure 6.1).

Related Video – ECG Rhythm Review – PVCs

Figure 6.1. Premature Ventricular Complex with Negative Deflection

QRS complex with a negative deflection followed by a T wave with a positive deflection.

A compensatory pause may follow the ectopic beat. The underlying rhythm continues uninterrupted because the impulse generated from the ventricles does not affect the impulses generated from the SA node, which continues to discharge at the expected time (see Figure 6.2).

Figure 6.2. Premature Ventricular Complex with Compensatory Pause

The compensatory pause following the PVC does not affect the underlying sinus rhythm because the SA node continues to discharge at its own pace.

PVCs can also occur without a compensatory pause. It is possible for the PVC to “squeeze” in-between two regular complexes without disturbing the regular pattern of the SA node. These PVCs are known as interpolated premature ventricular complexes.

PVCs indicate myocardial irritability. The frequency of occurrence of these abnormal ventricular beats is thus important to evaluate. If a patient has 5–10 PVCs within 1 minute, the PVCs are likely to be pathologic. Chest pain that is associated with the production of PVCs is likely life-threatening.