Atrial induction of ventricular tachycardia: reentry versus triggered automaticity.

Atrial stimulation induced a sustained ventricular tachycardia in two patients with mitral valve prolapse and in one patient who had mild hypertension without cardiac abnormalities. Exercise-induced sinus tachycardia also started the ventricular tachycardia in one patient. Evidence is presented to suggest that the mechanism of ventricular tachycardia in one patient was reentrant excitation and in another patient triggered automaticity. It is likely that the origin of the ventricular tachycardia was confined to a relatively protected small area near the posteroinferior portion of the left ventricle and was not due to macroreentry.