AIM: The baroreflex is a key mechanism in cardiovascular regulation and alterations in baroreceptor function are seen in many diseases, including heart failure, obesity and hypertension. We propose a new method for analyzing baroreceptor function from continuous blood pressure and heart rate in both health and disease.

METHODS: 48-hour data series of blood pressure and heart rate were collected with telemetry. Sprague-Dawley rats on standard chow (n=11) served as controls, while rats on a high-fat, high-fructose diet (n=6) constituted the obese-hypertensive model. A third group of rats underwent autonomic blockade (n=6). An autoregressive-moving-average with exogenous inputs (ARMAX)-model was applied to the data and compared with the α-coefficient.

RESULTS: Autonomic blockade caused a significant reduction in the strength of the baroreflex as estimated by ARMAX (ARMAX-BRS -0.03±0.01 vs. -0.19±0.04 bpm heartbeat-1). Both methods showed a ~50% reduction in BRS in the obese-hypertensive group compared with control (body weight 531±27 vs. 458±19 g, p<0.05; mean arterial pressure 119±3 vs. 102±1 mmHg, p<0.05; ARMAX-BRS -0.08±0.01 vs. -0.15±0.01 bpm heartbeat-1, p<0.05; α-coefficient-BRS 0.51±0.07 vs. 0.89±0.07 ms mmHg-1, p<0.05). The ARMAX-method additionally showed the open-loop-gain of the baroreflex to be reduced by ~50% in the obese-hypertensive group (-2.3±0.3 vs. -4.1±0.3 bpm, p<0.05), while the rate constant was similar between groups.

CONCLUSION: The ARMAX-model represents an efficient method for estimating several aspects of the baroreflex. The open-loop-gain of the baroreflex was attenuated in obese-hypertensive rats compared with control, while the time response was similar. The algorithm can be applied to other species including humans. This article is protected by copyright. All rights reserved.