INDUCED VENTRICULAR ARRHYTHMIAS IN REGIONALLY DENERVATED PORCINE HEART WITH HEALED MYOCARDIAL-INFARCTION

Study objective - The aim was to test the hypothesis that chronic sympathetic denervation of the boundaries of a healed myocardial infarction may modify the arrhythmogenic response to programmed electrical stimulation. Design - Electrical induction of ventricular arrhythmias and infarct size were evaluated in a control group of pigs with a one month old myocardial infarction induced by ligature of the left anterior descending coronary artery below the first diagonal branch. These were compared with a group of similarly infarcted pigs subjected to regional denervation of the peri-infarction area induced by topical pericoronary application of phenol. Denervation was verified by the absence of adrenergic histofluorescent reaction to glyoxylic acid in myocardial samples. Experimental material - 24 pigs (weight 15-20 kg) with myocardial infarction were studied, 13 of which were subjected to regional peri-infarction denervation, and 11 acted as controls. Measurements and main results - Programmed ventricular stimulation with one to four extrastimuli at 500 and 400 ms basic cycle length at the left and right ventricles induced fewer episodes of ventricular fibrillation in the denervated than in the non-denervated group (five episodes in three pigs v 14 in nine pigs, p < 0.005), but more episodes of sustained ventricular tachycardia (79 in eight pigs v 23 in two, p < 0.001). Unlike fibrillation, induction of ventricular tachycardia increased with multiple extrastimuli and with short basic cycle length. The denervated preparations tended to develop smaller infarcts but this difference was not statistically significant: infarct weight (g) relative to total ventricular mass (g) = 7.2 (SD 2.4)% v 10.5(4.5)%. Conclusions - Neural integrity of the non-ischaemic myocardium bordering a healed infarction modulates inducibility of ventricular tachycardia and fibrillation during programmed ventricular stimulation.