Inducibility of sustained ventricular tachycardia in a closed-chest ovine model of myocardial infarction

(T)he two goals of this study were(1) to develop a closed-chest animal mode l of monomorphic ventricular tachycardia; and (2) to investigate the effect of dual site pacing on inducibility of ventricular tachycardia. In the fir st part of the study, 10 of 14 sheep underwent successful induction of myoc ardial infarction by temporary balloon occlusion of the left anterior desce nding coronary artery After a follow-up period of 21-43 days, sustained mon omorphic ventricular tachycardia could be induced during programmed electri cal stimulation using a "clinical" stimulation protocol in 8 of the 10 shee p. The number of ventricular tachycardia episodes per animal varied between 5 and 70. Ventricular fibrillation wars never induced during programmed el ectrical stimulation. Ventricular tachycardia episodes lasted from 30 secon ds up to 15 minutes and were terminated by antitachycardia pacing or DC car dioversion. In the second part of the study, the effect of dual site stimul ation on ventricular tachycardia inducibility was investigated. High curren t stimuli from an area within the infarcted zone were given with the SI pro grammed stimulation protocol. This dual site stimulation showed no effect o n ventricular tachycardia induction during programmed electrical stimulatio n. This animal model shows a high induction rate of sustained monomorphic v entricular tachycardia in the chronic phase of myocardial infarction. The h igh incidence of ventricular tachycardia inducibility provides a reliable t ool to study new techniques for the prevention of ventricular tachyarrhythm ias.