Third-degree AV block — illustrated ventricular escape

Complete atrioventricular dissociation · regular P waves · independent slow escape rhythm · wide abnormal QRS in this example

Third-degree AV block with an illustrated ventricular escape Regular atrial impulses continue, but none conduct to the ventricles. An independent slow escape rhythm generates wide abnormal QRS complexes with secondary ST–T discordance. The animation illustrates a distal conduction block and a ventricular escape focus with activation from right ventricle toward left ventricle. A surface Lead II tracing cannot confirm the exact block or escape-focus site. The displayed rates are illustrative. Starting… Illustrated sequence: distal conduction block + ventricular escape · exact anatomical sites cannot be confirmed from Lead II alone RA LA RV LV SA ✓ AV ✕ Ventricular escape Illustrated AV transit ✓ Illustrated distal path Illustrated distal block ✕ Illustrated non-conduction Atrial rate: ~97 bpm* Escape rate: ~26 bpm* *Illustrated values Lead II — regular P waves · slower independent wide QRS complexes · secondary ST–T discordance · no consistent PR relationship ↔ Wide QRS (ventricular escape) P QRS T↕discordant

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.

What the tracing establishes. P waves and QRS complexes continue at independent regular rates with no consistent PR relationship. The atrial rate is faster than the ventricular escape rate, demonstrating complete atrioventricular dissociation.

What the animation assumes. The diagram places the block in the distal conduction system and the escape focus in the right ventricular myocardium. These sites and the RV-to-LV activation path are illustrative; they cannot be localised precisely from this Lead II tracing.

Escape morphology. This illustrated escape rhythm produces wide abnormal QRS complexes with secondary ST–T discordance. A slower, wider escape may suggest a more distal origin, but rate and QRS width alone do not reliably determine the anatomical site, stability or prognosis. The displayed atrial and escape rates are animation values, not reference ranges.

Clinical significance. Complete AV block is potentially life-threatening and warrants urgent veterinary assessment. Clinical signs, perfusion, ventricular rate, pause duration, escape stability, concurrent arrhythmia and underlying disease guide immediate management. Permanent pacing should be strongly considered in affected dogs, with decisions made through complete patient assessment and cardiology consultation.

Watch. The blue atrial impulses continue regularly but do not activate the ventricles. The independent amber escape focus periodically depolarises the ventricles, producing the slow wide-complex rhythm.
Educational illustration only. This animation simplifies cardiac conduction and is not a diagnostic ECG, treatment recommendation, or substitute for complete ECG interpretation, patient assessment or veterinary clinical judgement.
Third-degree AV block with ventricular escape · Widget v2 education edition · 23 August 2026 · Vet Detective cardiology animation library