Ventricular escape beat

It indicates a failure of the electrical conduction system of the heart to stimulate the ventricles (which would lead to the absence of heartbeats, unless ventricular escape beats occur).

[1] An escape beat usually occurs 2–3 seconds after an electrical impulse has failed to reach the ventricles.

Ventricular pacemaker cells discharge at a slower rate than the SA or AV node.

[citation needed] The escape arrhythmia is a compensatory mechanism that indicates a serious underlying problem with the SA node or conduction system (commonly due to heart attack or medication side effect), and because of its low rate, it can cause a drop in blood pressure and syncope.

For a patient with a ventricular escape beat, the shape of the QRS complex is broader as the impulse can not travel quickly via the normal electrical conduction system.

Animation illustrating the normal activation of the electrical conduction system of the heart : starting from the sinoatrial node , an electrical impulse spreads across the atria , then passes through the atrioventricular node (AV node) and conducts on via the bundle branches towards the ventricles .
The first 2.5 seconds show a normal cardiac cycle. This is followed by a period of delayed sinus activity which initiates a takeover response by the ventricular pacemaker cells resulting in a ventricular escape beat. Two escape beats are shown between 5-8 seconds.