What is the primary cause of premature ventricular contractions (PVCs)?

Premature ventricular contractions (PVCs) primarily occur due to ectopic impulses originating in the ventricles. This means that instead of the normal electrical conduction pathway leading to a heartbeat, an impulse arises from a place within the ventricles, causing them to contract earlier than expected. This ectopic activity disrupts the regular rhythm of the heart and often results in an irregular heartbeat sensation.

In a typical heartbeat, electrical impulses originate from the sinoatrial (SA) node and travel through the atria, then pass through the atrioventricular (AV) node before traveling down the ventricles. When a PVC occurs, this process is interrupted by impulses that are generated aberrantly in the ventricles themselves, creating an early contraction and a compensatory pause in the normal rhythm as the heart resets itself.

Other options listed may pertain to various heart conditions but do not explain the mechanism behind PVCs. For example, reentry circuits in the atria primarily affect atrial rhythms and would lead to conditions such as atrial fibrillation or flutter, not PVCs. A conduction delay in the AV node relates to the delay of impulses from the atrium to the ventricle but does not cause early ventricular contractions. While myocardial ischemia can provoke ect