Attenuated Heart Rate Recovery is Associated with Sympathetic Hyperactivity in Patients with Metabolic Syndrome and Obstructive Sleep Apnea

Abstract

Obstructive sleep apnea (OSA) and metabolic syndrome (MetS) are independently associated with impaired heart rate recovery (HRR) after maximal exercise. We tested the hypotheses that: 1) MetS+OSA would have an additive effect on attenuation of HRR; 2) The sympathetic hyperactivation would be involved on slower HRR. Newly diagnosed MetS (ATP III) patients, sedentary were divided into: MetS+OSA (n=18, 49±2y) and MetS-OSA (n=21, 44±2y). Normal individuals were also studied (C, n=13, 47±2y). OSA was characterized by apnea-hypopnea index (AHI) >15events/h (polysomnography). Muscle sympathetic nerve activity (MSNA, microneurography), heart rate (EKG), low (LF) and high (HF) frequency power bands and sympatho-vagal balance (LF/HF-Spectral analysis) were measured. The HRR was calculated (HRpeak minus HHR at 1st, 2nd, 4th min). MetS+OSA had higher MSNA, LF and LF/HF compared with MetS-OSA and C. MSNA was higher in MetS-OSA than in C. HF power was lower in MetS+OSA compared with MetS-OSA and C. HRR at 1st, 2nd min was lower in MetS+OSA compared with C (P<0.01) and lower at 4th min compared with Met-OSA and C (P<0.01). Further analyses showed an association between MSNA levels and HRR (P<0.01). In conclusion, OSA exacerbates the attenuation of HRR after maximal exercise in patients with MetS. In addition, the attenuation of HRR is associated with sympathetic hyperactivation.