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PREMATURE VENTRICULAR CONTRACTION (PVC) in an otherwise normal ELECTROCARDIOGRAM (ECG or EKG). Normally, the heartbeat is initiated by an electrical impulse from the Sinoatrial Node (Pacemaker). A PVC is initiated by Purkinje Fibers (the last part of the conduction system) in the ventricles. A PVC occurs before you expect the next heart cycle (P, QRS, and T waves) hence the word premature. PVC's have a much different shape and show a large electrical change (high voltage QRS complex) in the ECG. A person may perceive a stronger or skipped heart beat or palpitations. PVC's can even occur in healthy persons and there are multple causes--even excessive caffeine. Very frequent PVC's may be associated with underlying heart conditions. Terms like Ectopic Beats or Extrasystoles are sometimes sometimes used in association with PVC's.