Ventricular premature complex — illustrated LV origin

Premature ventricular activation · wide abnormal QRS · secondary ST–T discordance · compensatory pause in this example

VPC from an illustrated left ventricular origin with a compensatory pause Two sinus complexes are followed by a premature ventricular complex arising from the illustrated left ventricular free-wall focus. The animation shows slow myocardial activation from left ventricle toward right ventricle, producing a wide abnormal QRS and a secondary discordant T wave. In this example, the sinus node is not reset and a full compensatory pause follows. Starting… RA LA RV LV SA AV LV focus AV node Bundle of His This animation contrasts illustrated LV→RV and RV→LV activation. Clinical localisation requires multiple leads; Lead II polarity alone is insufficient. Lead II — NSR → NSR → premature wide QRS → compensatory pause → NSR Beat 1 Beat 2 VPC ↑ expected P* · refractory ← full compensatory pause → Beat 3 wide abnormal QRS — illustrated LV→RV activation

Paused at the start of the animation.

0.25×

The default 0.25 times setting is a slow teaching speed. It does not represent a physiological heart rate.

Controls. Use Play or Pause, Reset, or the speed slider. The default 0.25× setting is a slow teaching speed and does not represent a physiological heart rate.

Illustrated LV origin. The ectopic focus is drawn in the LV free wall and activation moves from LV toward RV, producing a wide abnormal QRS. RBBB-like morphology across appropriate leads supports a probable LV origin, but the exact site cannot be determined from Lead II alone.

What the tracing shows. The complex occurs prematurely, is not consistently preceded by a related P wave, has a wide abnormal QRS and shows secondary ST–T discordance. The predominantly negative Lead II QRS is a feature of this illustrated axis, not every LV-origin VPC.

Full compensatory pause. In this sequence, the VPC does not reset the sinus node. The next expected sinus impulse arrives while the conduction system or ventricles remain refractory and is not followed by a ventricular complex. The interval between the sinus complexes surrounding the VPC equals two baseline R–R intervals. Not every VPC is followed by a full compensatory pause.

Clinical interpretation. Morphology may suggest the site of origin but does not establish the cause or clinical significance. Interpret the rhythm in the context of signalment, clinical signs, structural or systemic disease, ectopic burden, complexity and haemodynamic effect.
Educational illustration only. This animation simplifies cardiac activation and is not a diagnostic ECG, treatment recommendation, or substitute for assessment of a complete clinical tracing.
VPC — LV origin · Widget v2 education edition · 23 August 2026 · Vet Detective cardiology animation library