A method for assessment of the dynamic response of the arterial baroreflex

AimThe 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 analysing baroreceptor function from continuous blood pressure (BP) and heart rate (HR) in both health and disease. MethodsForty-eight-hour data series of BP and HR were collected with telemetry. Sprague Dawley rats on standard chow (n = 11) served as controls, while rats on a high-fat, high-fructose (HFHC) 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 -coefficient. ResultsAutonomic blockade caused a significant reduction in the strength of the baroreflex as estimated by ARMAX [ARMAX- baroreflex sensitivity (BRS)] -0.03 0.01 vs. -0.19 +/- 0.04 bpm heartbeat(-1)). Both methods showed a similar to 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; -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 similar to 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. ConclusionThe 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.