Cardiac sympathetic activity assessed by heart rate variability indicates myocardial ischemia on cold exposure in diabetes

Abstract

PurposeCold exposure is one of the major risk factors for cardiac events in diabetes. The aim of this study is how cardiac sympathetic nerve activity (SNA) is affected by temporal cold exposure in diabetes using heart rate variability (HRV).MethodsMale Wistar Rat (n=12) were divided into two groups: Control and Diabetes. Diabetes was induced by streptozocin. Lower extremity was sprayed for cold vapor for 5 seconds. Rectal and subcutaneous tissue temperature, flow velocity of lower extremity using laser Doppler flow meter, frequency domain analysis of HRV and ST change were measured up to 15 min from initial cold exposure.ResultsSNA was able to define as a power between 0 and 0.2 Hz in HRV by use of propranolol (60mg/kg). SNA was enhanced in diabetes than control (p<0.05) associated with reduction of blood flow (p<0.05). SNA was decreased by cold exposure in control (p<0.005), however, diabetes did not show significant reduction. SNA was enhanced significantly in diabetes at 1, 5, 10 and 15 min after cold exposure compared with control (p<0.01, p<0.005, p<0.05, p<0.0005, p<0.01, respectively). ST change was significantly larger in diabetes than control in 1 and 5 min after cold exposure (p<0.001, p<0.005).ConclusionCardiac SNA was decreased after cold exposure to lower extremity in control. In contrast, cardiac SNA was enhanced in diabetes than control, which may lead to cardiac ischemia in cold exposure in diabetes.