Abstract 19352: Obstructive Sleep Apnea Impairs the Time Delay of the Baroreflex Control and the Oscilattory Pattern of the Sympathetic Activity in Patients with Metabolic Syndrome
Background: Incidence and oscillatory pattern of muscle sympathetic nerve activity (MSNA) depends on the magnitude (sensitivity) and time delay of the arterial baroreflex. In metabolic syndrome (MetS), the obstructive sleep apnea (OSA) exacerbates the MSNA and baroreflex control of heart rate. Unknown is the impact of MetS and OSA on oscillatory pattern of MSNA and time delay of the baroreflex control of MSNA in MetS patients. We tested the hypotheses that: 1) MetS would impair these autonomic functions; 2) OSA would impair even further these autonomic functions.
Methods and Results: Thirty-nine never-treated MetS patients (ATP III) were allocated in two groups according to the presence of OSA (MetS+OSA, n=17 and MetS-OSA, n=22). Twelve aged-paired healthy subjects were enrolled in the study as control group (C). OSA (apnea-hypopnea index>15 events/hour) was determined during a polysomnography. We recorded MSNA (microneurography), blood pressure (beat-to-beat basis) and HR (ECG), during 10 min. Oscillatory patterns of MSNA, HR and systolic arterial pressure were evaluated by autoregressive spectral analysis. The baroreflex control of MSNA (gain and time delay), were evaluated by bivariate autoregressive analysis. Patients with MetS+OSA had increased high frequency band of MSNA (HFMSNA, 60±3 vs. 49±2 and 37±2 n.u., P<0.001) and decreased low frequency band of MSNA (LFMSNA, 40±3 vs. 51±2 and 63±2 nu, P<0.001) compared to MetS-OSA and C. The gain of the baroreflex control of MSNA was lower in MetS+OSA compared MetS-OSA and C (13±1 vs. 30±3 and 43±3 a.u./mmHg, P<0.001). The time delay of the baroreflex control of MSNA was augmented in MetS+OSA compared to MetS-OSA and C (6±0.3 vs. 4±0.3 and 3±0.2 s, P<0.001). MetS-OSA patients showed increased HFMSNA (P<0.001) and decreased LFMSNA (P<0.001) compared with C. And, the gain of the baroreflex control of MSNA was lower in MetS-OSA than in C groups (P<0.001).
Conclusions: MetS reduces the oscillatory pattern of MSNA and the gain of the baroreflex control of MSNA. OSA exacerbates these dysfunctions and further increases the time delay of the baroreflex control of MSNA in these patients. These central autonomic dysregulation of sympathetic modulation may have important clinical implications in patients with MetS+OSA.
- © 2012 by American Heart Association, Inc.