Premature ventricular contraction irregular heartbeat ventricular premature beat premature ventricular contraction extrasystole MP:0009732 MPheno.ontology PVC ventricular premature contraction ventricular ectopic beat premature ventricular complex VPC VPB a heartbeat is initiated by abnormal electrical activation originating in the heart ventricles rather than by the sinoatrial node, the normal heartbeat initiator, before a normal heartbeat would occur premature ventricular contraction; ventricular premature beat