Antiarrhythmic actions of left stellectomy in digitalis-mediated malignant ventricular arrhythmias in the postinfarcted canine heart

Abstract

Recently, this laboratory has demonstrated an enhanced susceptibility toward the development of ischemia-related lethal ventricular arrhythmias in the presence of therapeutic serum concentrations of digoxin in conscious dogs after myocardial infarction. The present study was performed to assess the effect of the interruption of cardiac sympathetic influences, via subacute left stellate ganglionectomy (LSGX), on digitalis-mediated ischemic ventricular arrhythmias. Commencing 4-5 days after anterior myocardial infarction, 11 dogs with LSGX and 14 sham controls were administered digoxin (0.0125 mg/kg/day i.v.) for 5-7 consecutive days. At baseline testing, programmed ventricular stimulation failed to initiate ventricular tachycardia in any postinfarction dog entered into this evaluation. After treatment, 11/11 digoxin + LSGX (1.33 +/- 0.10 ng/ml serum digoxin) and 14/14 digoxin-treated sham (1.23 +/- 0.14 ng/ml serum digoxin) dogs remained nonresponsive to programmed stimulation testing. The incidence of arrhythmic mortality in response to subsequent ischemia at a site remote from the infarcted anterior region was greater in the digoxin-treated sham group (1.22 +/- 0.21 ng/ml serum digoxin) than in the digoxin + LSGX group (1.33 +/- 0.10 ng/ml serum digoxin); mortality was 6/10 (60%) digoxin sham vs. 1/10 (10%) digoxin + LSGX, p less than 0.005. The underlying anterior myocardial infarct sizes (% of left ventricle: 6.8 +/- 2.3 vs. 6.6 +/- 1.1) did not differ between the digoxin sham and digoxin + LSGX groups. However, the digoxin sham controls developed larger posterolateral myocardial infarctions than did the digoxin + LSGX animals (% of left ventricle: 27.4 +/- 3.0 vs. 16.7 +/- 2.7, p less than 0.05). Norepinephrine concentrations in posterolateral through posteroseptal ventricular sections were not altered by LSGX in a separate group of digoxin-treated postinfarct dogs. The results suggest that left stellate ganglionectomy may reduce the incidence of digitalis-mediated malignant ventricular arrhythmias during ischemia, possibly due to a reduction in the severity of ischemic injury.