Ventricular tachycardia is a potentially lethal arrhythmia that can compromise the pumping ability of the ventricles. During ventricular tachycardia, the ventricular rate can rise from the normal 60-100 beats per minute to 160-240 beats per minute.

A common mechanism by which ventricular tachycardia can arise is the continuous reactivation of an electrical circuit in the ventricles, which can appear as a three-dimensional spiral wave of electrical activity that recirculates within the ventricles with a period of about 200 to 300 ms. The rapid rate causes the ventricles to contract too quickly to maintain adequate blood output. Typically, the atria continue to function normally, with regular bioelectrical waves initiated by the heart's natural pacemaker.

Ventricular tachycardia can occur in the absence of apparent heart disease, and it often can develop very quickly into a more immediately life-threatening arrhythmia, ventricular fibrillation.