Short-term vagal nerve stimulation improves left ventricular function following chronic heart failure in rats

Abstract

Increasing numbers of animal and clinical investigations have demonstrated the effectiveness of long-term electrical vagal nerve stimulation (VNS) on chronic heart failure (CHF). The present study investigated the effects of short-term VNS on the hemodynamics of cardiac remodeling and cardiac excitation-contraction coupling (ECP) in an animal model of CHF following a large myocardial infarction. At 3 weeks subsequent to ligation of the left coronary artery, the surviving rats were randomized into vagal and sham-stimulated groups. The right vagal nerve of the CHF rats was stimulated for 72 h. The vagal nerve was stimulated with rectangular pulses of 40 ms duration at 1 Hz, 5 V. The treated rats, compared with the untreated rats, had significantly higher left ventricular ejection fraction (54.86 ± 9.73, vs. 45.60 ± 5.51%; P=0.025) and left ventricular fractional shortening (25.31 ± 6.30, vs. 15.42 ± 8.49%; P=0.013), and lower levels of brain natriuretic peptide (10.07 ± 2.63, vs. 19.95 ± 5.22 ng/ml; P=0.001). The improvement in cardiac pumping function was accompanied by a decrease in left ventricular end diastolic volume (1.11 ± 0.50, vs. 1.54 ± 0.57 cm(3); P=0.032) and left ventricular end systolic volume (0.50 ± 0.28, vs. 0.87 ± 0.36 cm(3); P=0.007). Furthermore, the expression levels of ryanodine receptor type 2 (RyR2) and sarcoplasmic reticulum calcium adenosine triphosphatase (SERCA2) were significantly higher in the treated rats compared with the untreated rats (P=0.011 and P=0.001 for RyR2 and SERCA2, respectively). Therefore, VNS was beneficial to the CHF rats through the prevention of cardiac remodeling and improvement of cardiac ECP.