Osmosis video - Premature ventricular contraction

Premature ventricular contractions are abnormal heartbeats that originate in the ventricles and show up as tall and wide QRS complexes on an ECG. They occur when an extra beat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node, the normal heartbeat initiator. PVCs are usually asymptomatic, but when they're a sign of an underlying disorder, treatment including a radiofrequency ablation may be necessary.