Short Term Effect of Bariatric Surgery Induced Weight Loss on Cardiac Autonomic Function

Abstract

A primary metabolic alteration with obesity is insulin resistance (IR), which has been shown to be associated with impaired cardiac autonomic function. Considering recent work indicating marked improvements in IR as little as three weeks following bariatric surgery, we sought to determine whether such improvements in IR were accompanied by favorable alterations in cardiac autonomic control. Six patients (42±3 yr) were studied before and one month following Roux‐en‐Y gastric bypass surgery. Beat‐to‐beat heart rate and blood pressure (BP) were measured to assess heart rate and BP variability (power spectral analysis) and estimate spontaneous cardiac baroreflex sensitivity (transfer function gain, 0.04–0.15 Hz). Insulin resistance was estimated with the homeostasis model assessment (HOMA) index. Following surgery body mass index (53±3 pre vs. 47±3 post kg/m2), blood glucose, and HOMA (7.2±1.4 pre vs. 5.1±0.9 post) were all significantly reduced (P<0.05 pre vs. post). In contrast, low and high frequency heart rate variability, low frequency BP variability, and cardiac baroreflex sensitivity (6.3±1.4 pre vs. 7.4±2.1 post ms/mmHg; P=0.43) were unchanged. These preliminary findings suggest that despite marked reductions in body weight and improvements in insulin resistance one month following bariatric surgery, cardiac autonomic function and baroreflex sensitivity are unaltered.