Abstract 4150: Exercise Training Restores Baroreflex Control of Sympathetic Nerve Activity in Hypertensive Patients
Introduction: Previous studies demonstrated that exercise training improves the baroreflex control of heart rate in hypertensive patients. However, the effects of exercise training on baroreflex control of sympathetic nerve activity in hypertensive patients are unknown. We tested the hypothesis that exercise training would improve baroreflex control of muscle sympathetic nerve activity (MSNA) in untreated hypertensive patients.
Methods: Eighteen mild-to-moderate hypertensive patients were selected to represent two groups: Exercise trained (n=11, 46±2yr) and untrained (n=7, 45±3yr). An additional age-matched normo-tensive exercise trained group (n=12, 42±2yr) was also studied. Baroreflex sensitivity of MSNA(microneurography) was assessed by stepwise i.v. infusions of phenylephrine and sodium nitroprusside, and analyzed by linear regression. Blood pressure (BP) was non-invasively monitored on a beat-to-beat basis.
Results: Baseline BP and MSNA were similar between hypertensive groups, but significantly increased when compared with normotensive controls. Baroreflex control of MSNA was similar between hypertensive groups, but significantly lower than normotensive controls. In hypertensive patients, exercise training significantly reduced MSNA (P<0.05) and BP (P<0.01) and significantly increased baroreflex control of MSNA during increases (0.53±0.1 vs 1.06±0.2 bursts/min/mmHg, P<0.01) and decreases (0.79±0.2 vs 2.14±0.3 bursts/min/mmHg, P<0.01) in mean BP. In addition, the difference in baroreflex control sensitivity of MSNA between hypertensive patients and normotensive controls was no longer observed (P=0.99 and P=0.99, respectively). No significant changes were found in untrained hypertensive patients.
Conclusions: Exercise training restores baroreflex control of MSNA in untreated hypertensive patients. This improvement in baroreflex sensitivity may explain the reduction of BP after exercise training in hypertension.