Assessment of cardiac autonomic function by post exercise heart rate recovery in diabetics

Background and Aims: Autonomic dysfunction in type 2 diabetes mellitus (DM) patients may translate into an increased cardiovascular morbidity and mortality. Autonomic system regulates 'heart rate recovery' (HRR), an important predictor of cardiovascular mortality, which can be assessed using the exercise electrocardiogram (ECG). Hence, utilizing HRR, this study assessed the autonomic function of the cardiovascular system after one minute of exercise stress test in both, patients with and without type 2 DM. Materials and Methods: A prospective case control study involving 50 patients with type 2 DM and 50 without type 2 DM, matched for age and sex, was carried out. Each subject underwent an exercise stress test by treadmill using the Bruce protocol. Cardiovascular parameters like heart rate was recorded using a 12 lead ECG along with blood pressure. Results: Patients with T2DM had lesser HRR after exercise (p < 0.001). Exercise capacity was significantly reduced among patients with T2DM when compared to controls (p = 0.01). A multiple linear regression analysis (R2=0.26) revealed that duration of diabetes (β=-0.02, p=0.048) and resting systolic blood pressure (SBP) (β=- 010, p=0.048) are independent predictors of HRR. Conclusion: The study revealed HRR to be significantly reduced among patients with type 2 DM. HRR may hint at the presence of cardiac autonomic dysfunction and predict the cardiovascular mortality.