Vagus Nerve Stimulation In Hypertensive Rats: Assessing Pathophysiology Using ECG And Pressure Data

Abstract

Hypertension, which is associated with an imbalanced autonomic nervous system, is becoming an increasing problem in the US and worldwide, and new therapies are needed, since not all patients respond to current medications. Vagus nerve stimulation (VNS), which aims to restore autonomic balance, has emerged as a promising new treatment for this disease. In our lab, we conducted an experimental study aimed at assessing the safety and efficacy of chronic, continuously cyclic VNS to attenuate the development of hypertension in spontaneously hypertensive rats. Hypertension was induced via a high salt diet and rats were randomized into two groups: Sham Control (n=6) and VNS Treatment (n=6). In vivo blood pressure and electrocardiogram (ECG) were monitored continuously by an implantable telemetry system. We developed and validated methods to calculate time and frequency domain metrics for heart rate variability and blood pressure variability. Additionally, the sequence method in the time domain was employed to measure baroreflex sensitivity. Artifacts and ectopic beats can cause errors in the analysis of these metrics, so we also developed and validated robust pre-processing methods to edit ECG and pressure data in order to acquire clean signals. Results show that hypertension leads to decreased heart rate variability, decreased baroreflex sensitivity, and increased blood pressure variability, all of which are indicative of pathophysiological effects of hypertension. VNS may preserve heart rate variability blood pressure variability and baroreflex sensitivity at certain frequencies.