Vagal nerve stimulation (VNS) induces bradycardia in chronic heart failure (CHF). We hypothesized that beta-blocker would cover the beneficial effects of VNS on CHF if the anti-beta-adrenergic effect was the main VNS effect. This study investigated the effects of VNS on cardiac remodeling in rats with CHF treated with metoprolol. Two weeks after myocardial infarction, surviving rats were randomly assigned to groups of sham stimulation (SS), sham stimulation with metoprolol (SSM), or VNS with metoprolol (VSM). Compared to the SS group, heart rate was significantly reduced in the SSM and VSM groups. Hemodynamic assessments showed that VSM rats maintained better cardiac pump function and presented higher cardiac index and lower heart weight than SSM rats. VSM was also associated with lower plasma brain natriuretic peptide and norepinephrine levels than SSM. VSM but not SSM improved the 50-day survival rate compared with the SS group. The results suggest that VNS may exert its beneficial effects on the failing heart independently of its anti-beta-adrenergic mechanism.
Keywords: Beta-blocker; Cardiac remodeling; Chronic heart failure; Myocardial infarction; Vagal nerve stimulation.