Pathophysiology
Normally impulses pass through both ventricles almost simultaneously and the depolarization waves of the two ventricles partially cancel each other out in the ECG. However, when a PVC occurs the impulse nearly always travels in one direction, so there is no neutralisation effect; this results in the high voltage QRS wave in the electrocardiograph.
There are two main physiological explanations for premature ventricular contractions: re-entrant signalling and “enhanced automaticity in some ectopic focus”. The enhanced automaticity means that the ectopic centre fires more regularly than usual and is protected from depolarisation that results in premature contractions.
Read more about this topic: Premature Ventricular Contraction