Effects of Low Frequency Electrical Stimulation in Baroreflex Sensitivity and Heart Rate Variability in Rats with Heart Failure

The low frequency electrical stimulation (ES) promotes an improvement of functional capacity in patients with heart failure (HF), with unclear action mechanisms. The goal of the present study was to evaluate the effects of ES on the arterial baroreflex sensitivity (BRS) and cardiovascular autonomic control in rats with HF. Male Wistar rats were assigned to one of four groups: placebo sham (P-Sham, n = 9), ES sham (ES-Sham, n = 9), placebo HF (P-HF, n = 9) or ES HF (ES-HF, n = 9). The ES was adjusted at a low frequency (30 Hz), duration of 250 μs, with hold and rest time of 8 s (4 wks, 30 min/day, 5 times/wk). It was applied on the gastrocnemius muscle with intensity to produce a visible muscle contraction. The data were compared by a two-way ANOVA test and the post hoc Student-Newman-Keuls (p < 0.05). The BRS was higher in ES-Sham group compared to the P-Sham group and the ES-HF group compared to the P-HF group. ES was able to decrease heart rate sympathetic modulation in ES-HF compared to P-HF group and peripheral sympathetic modulation for the same groups. Interestingly, heart rate sympathetic modulation was similar between ES-HF and P-Sham groups. Thus, ES enhances heart rate parasympathetic modulation on infarction (ES-HF) compared to placebo (P-HF), with consequent improvement of sympathovagal balance in the ES-HF group compared to the P-HF. These findings show that a 4-wk ES protocol in HF rats promotes an improvement in arterial BRS, and cardiovascular autonomic control.