Harbingers of paroxysmal ventricular tachycardia in acute myocardial infarction.

We examined the harbingers of 68 episodes of paroxysmal ventricular tachycardia in 42 patients with documented acute myocardial infarction. Late ventricular premature contractions initiated 46 bouts of paroxysmal ventricular tachycardia, while 17 were engendered by early ventricular premature contractions and five by atrial premature contractions. Paroxysmal ventricular tachycardia related to early ventricular premature contractions tended to last longer and failed to respond to therapy with lidocaine more often than paroxysmal ventricular tachycardia begun by late ventricular or atrial premature contractions. Ventricular fibrillation occurred in six cases of paroxysmal ventricular tachycardia due to early ventricular premature contractions but was absent in paroxysmal ventricular tachycardia related to late ventricular or atrial premature contractions. The "malignant" potential of a given ventricular premature contraction cannot be assessed from its degree of prematurity alone.