The heart has an electrical system that allows it to contract and pump blood through the body in a coordinated rhythm. Regular heartbeats occur when specialized cells in the right atrium of the heart, called the sinoatrial (SA) node, conduct an electrical signal down to the atrioventricular (AV) node which is another set of specialized cells. This electrical signal then works its way down the bundle of His and Purkinje fibers to the heart ventricles. The result is the contraction of the ventricles and pumping of blood from the heart out to the body's arteries.

During a premature ventricular contraction (PVC), the heartbeat is initiated by the Purkinje fibers rather than the SA node. Given that a PVC occurs before a regular heartbeat, there is a pause before the next regular heartbeat.

PVCs can occur in isolation or in repeated patterns. Two consecutive PVCs are termed doublets while three consecutive PVCs are named triplets. It is important to note that three or more consecutive PVCs are classified as ventricular tachycardia. If the PVCs continuously alternate with a regular sinus beat, the patient is in bigeminy. Likewise, if every third heartbeat is a PVC, then it is named trigeminy.

PVCs present as heart palpitations in most patients. They are usually benign and do not require treatment.