Effects of Angiotensin II and Captopril on Inducible Sustained Ventricular Tachycardia Two Weeks After Myocardial Infarction in the Pig

The effects of angiotensin II (AII) and captopril (C) on the inducibility of ventricular tachyarrhythmias were investigated 14 days after infarction in pigs. In 27 pigs, ischemia was induced by 60-min occlusion of the left coronary artery. Four pigs died of ventricular fibrillation during ischemia, and six others died within 24 h due to pump failure. Of the 17 survivors, eight pigs developed a sustained (greater than 30 s) monomorphic ventricular tachycardia (sVT) after programmed electrical stimulation. In nine noninducible pigs, an AII infusion (0.6 microgram/kg/min) caused inducible sVT in three animals and nonsustained VT in two animals (greater than 10 reentrant beats). In two of the remaining four animals, spontaneous premature ventricular beats appeared during the infusion. In a group of five healthy pigs, the electrophysiological effects of AII were evaluated. Infusion of AII caused a rapid and sustained increase in arterial blood pressure to 161 +/- 6.4% (p less than 0.001). The sinus cycle length decreased to 74 +/- 5.2% (p less than 0.02). The effective refractory period of the right ventricle decreased significantly to 82 +/- 5.5% (p less than 0.05). These results show that modulation of the renin-angiotensin system after myocardial infarction influences the inducibility of malignant ventricular tachyarrhythmias, as shown by the increased inducibility of sustained ventricular tachycardia. This may be related to a decreased ventricular refractoriness. Therefore, it is suggested that C can reduce malignant ventricular tachycardia late after myocardial infarction by preventing the deleterious arrhythmogenic effects of AII.