The effects of bilateral and unilateral vagotomy on heart rate dynamics

Aim: It was aimed to investigate effects of right and/or left vagotomy on heart rate variability (HRV) in spontaneously breathing rats. It was hypothesized that linear and nonlinear methods of HRV may indicate different asymmetrical influence of parasympathetic nerve fibers to the heart. Material and Methods: In our study, 40 male Wistar rats were divided into 5 groups (n=8): 1. Control (Sham) Group, 2. Right vagotomy Group, 3. Left vagotomy group, 4. Bilateral vagotomy group, 5. Atropine Group (intraperitoneally injected 5 mg/kg). Urethane anesthesia (1.5 g/kg) was administered intraperitoneally before the intervention: All animals breathed spontaneously, during the simultaneous recordings of electrocardiograms (ECG) and breathing frequencies. Performed HRV analyses were frequency and time domain as linear HRV analyses, Poincare Plot, Detrended Fluctuation and Entropy analyses as non-linear analyses. Results: RR interval was decreased in Atropine and Bilateral groups and QJ interval was decreased in Right vagotomy group. Right and bilateral vagotomy prolonged QJc interval. Atropine and Bilateral vagotomy both changed time, frequency-based and nonlinear parameters. While Left vagotomy affected only frequency-based parameters, Right vagotomy affected time and frequency domain parameters but only in first 10 minutes. Nonlinear parameters were only affected by Atropine and bilateral vagotomy. Conclusion: Left vagotomy affected only frequency domain parameters. Right vagotomy changed both frequency and time domain parameters but only in first 10 minutes. This indicates right vagotomy triggered a possible hormonal reflex mechanism, but left vagotomy did not. Thus, it can be concluded that right and left Vagus affect HRV parameters asymmetrically.