Prematurity of an ectopy is determined by the intrinsic escape rhythm of the ectopic focus. For ventricular ectopy, an instantaneous rate of >40–50 beats per minute would be considered 'premature'.

Ventricular tachycardia is an abnormally fast heart beat (with three or more consecutive heart beats at least 100 beats per minute) that originates from one of the ventricles in the heart.