Short-term Heart Rate Variability to Evaluate Cardiovascular Autonomic Neuropathy in Newly Diagnosed Type 2 Diabetes Mellitus Patients: A Cross-sectional Study

Abstract

Introduction: Cardiovascular Autonomic Neuropathy (CAN) may be seen in patients of Type 2 Diabetes Mellitus (T2DM). In many previous studies it was seen that there is reduced heart rate variability in DM patients. Reduced heart rate variability is earliest indicator for the CAN. In different earlier studies, it was found that results of Short-term Heart Rate Variability (HRV) analysis of five minutes is comparable to standard 24 hours HRV analysis. In DM patients CAN is mostly found to be associated with a longer duration of disease, but according to some studies CAN may be present in newly diagnosed diabetes patients also, but the percentage is lower. Aim: To assess the short-term HRV profile as cardiovascular risks among newly diagnosed T2DM patients and to find the correlation of HRV parameters with duration of disease and biochemical parameters; Fasting Plasma Glucose (FPG) and Postprandial Plasma Glucose (PPPG) for early detection and management of CAN. Materials and Methods: The present study was a cross-sectional study conducted in the Department of Physiology in collaboration with the Department of Endocrinology at R.G. Kar Medical College and Hospital, Kolkata, West Bengal, India, from September 2020 to August 2021 on 56 newly diagnosed T2DM (age group 30 to 64 years). Study subjects were grouped according to the Standard deviation of NN intervals (SDNN) (millisecond) value as cardiovascular risk factor. Group 1 was the low risk group, group 2 was the moderate risk group, group 3 was the high-risk group. HRV testing was done with Physiograph Polyrite-D instrument with bio-amplifiers, 4 channels and accessories (RMS latest software-Version 3.0.16) in Autonomic Function Research Laboratory to measure HRV parameters. After collecting data, analysis was done using Statistical Package for Social Sciences (IBM, SPSS) version 23.0 Unpaired student’s t-test, Chi-square test, Analysis of Variance (ANOVA) test, Pearson correlation test were performed and statistical significance of different parameters were evaluated. It was considered statistically significant when p-value <0.05. Results: By assessing HRV parameters as cardiovascular risk factors among newly diagnosed T2DM patients the present study showed there was significantly (p-value=0.0065) high LF/HF ratio in males (1.70±1.19) than in females (0.99±0.69). The SDNN value was significantly highest in low cardiovascular risk group (137.29±25.49 ms) and lowest in high cardiovascular risk group (26.07±12.03 ms) (p-value=0.00001). Low Frequency and High Frequency Ratio (LF:HF ratio) was significantly more in age group of 51-60 years. Among all the patients, 34 (61%) patients had increased parasympathetic activity and 22 (39%) subjects had increased sympathetic activity. Female patients showed significantly more increased parasympathetic 24 (75%) activity than males 10 (41.7%). There was a significant association between SDNN values with the duration of disease (p-value=0.004). Conclusion: The present study showed that cardiac autonomic neuropathy is present even at the time of diagnosis of newly diagnosed T2DM as there was sympathovagal imbalance. Female patients have more parasympathetic drive than males which indicates that females are more cardioprotective.