Observations on mechanisms of ventricular tachycardia in man.

Fifty patients with sustained ventricular tachycardia were studied by endocavitary recordings and programmed electrical stimulation. Of 29 patients in whom tachycardia could be initiated, 18 had chronic coronary artery disease and eight had no detectable heart disease. Of 35 patients in whom the tachycardia could be terminated by premature ventricular stimuli, 21 had chronic coronary artery disease and eight had no detectable heart disease. Initiation of tachycardia was facilitated in 18 of 21 patients by pacing the ventricle at the slowest possible pacing rate. An inverse relation was found between the prematurity of the tachycardia-initiating premature beat and the interval between the premature beat and the first beat of tachycardia, a finding suggestive of a re-entry mechanism. The role of the specific conduction system in initiation and during tachycardia remains unknown. Stimulation site was found to affect initiation and termination of tachycardia and width of tachycardia zone.