Ventricular tachycardia is defined as three or more consecutive ventricular beats at a rate above 100 bpm.
Ventricular tachycardia usually occurs in a diseased heart.
The ventricular muscle depolarises at a high frequency, causing, in effect, rapidly repeated ventricular extrasystoles. The excitation spreads abnormally through the ventricular muscle, resulting in an abnormally wide QRS complex on the ECG.
Ventricular tachycardia may be a complication of myocardial infarction.