What is the role of ECG in the workup of premature ventricular contractions (PVCs)?

Updated: Jan 13, 2017
  • Author: James E Keany, MD, FACEP; Chief Editor: Erik D Schraga, MD  more...
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Answer

Electrocardiography (ECG) allows characterization of the ventricular ectopy and determination of the cause. In addition to the standard 12-lead ECG, a 2-minute rhythm strip may help in determining the frequency of the ectopy and capturing infrequent premature ventricular contractions (PVCs). Findings may include the following:

  • Left ventricular hypertrophy
  • Active cardiac ischemia (ST-segment depression or elevation and or T-wave inversion)
  • In patients with previous MI - Q waves or loss of R waves, bundle-branch block
  • Electrolyte abnormalities (hyperacute T waves, QT prolongation)
  • Drug effects (QRS widening, QT prolongation)

On ECG, PVCs may be premature in relation to the next expected beat of the basic rhythm. The pause after the premature beat is usually a fully compensatory one. The R-R interval surrounding the premature beat is equal to double the basic R-R interval, showing that the ectopic beat did not reset the sinus node. PVCs may appear in a pattern of bigeminy, trigeminy, or quadrigeminy (ie, may occur every other beat, every third beat, or every fourth beat). PVCs with identical morphologies on a tracing are called monomorphic or unifocal. PVCs demonstrating two or more different morphologies are referred to as multiform, pleomorphic, or polymorphic. (See the images below.)

ECG shows frequent, unifocal PVCs with a fixed cou ECG shows frequent, unifocal PVCs with a fixed coupling interval between the ectopic beat and the previous beat. These PVCs result in a fully compensatory pause; the interval between the 2 sinus beats surrounding the PVC are exactly twice the normal R-R interval. This finding indicates that the sinus node continues to pace at its normal rhythm despite the PVC, which fails to reset the sinus node.
On this ECG, the PVCs occur near the peak of the T On this ECG, the PVCs occur near the peak of the T wave of the preceding beat. These beats predispose the patient to ventricular tachycardia or fibrillation. This R-on-T pattern is often seen in patients with acute myocardial infarction or long Q-T intervals. In the latter case, the triggered arrhythmia would be torsade.

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