Exploring the relationship of cardiac autonomic function and rate-pressure product in individuals with type 2 diabetes mellitus

Background Cardiac autonomic neuropathy (CAN) is one of the most ignored complications of type 2 diabetes mellitus (T2DM). One of the indicators of CAN is a low heart rate variability (HRV). Rate-pressure product (RPP) indicates myocardial oxygen consumption. Theoretically, a reduction in HRV (due to increased resting HR (> 100 bpm) in T2DM) will lead to an increase in the resting RPP and, thereby, myocardial blood flow and oxygen consumption. However, no numerical relationship has been established. The objective of the present study was to examine the relationship between the cardiac autonomic function and RPP in individuals with T2DM. Methods The study was a cross-sectional study in individuals with type 2 diabetes mellitus, between 40 and 65 years. The participants underwent HRV analysis (a measure of cardiac autonomic function) as per standard guidelines. RPP was calculated using the resting heart rate and resting systolic blood pressure. The normality of the data was checked using the Shapiro-Wilk p test and visual analysis of histograms. Correlation between the RPP and the HRV measures was performed using Spearman’s correlation (rho). Multiple linear regression was conducted using RPP and HRV parameters (RMSSD and LF/HF). P-value was considered statistically significant if less than 0.05. Results A total of 90 participants were screened; 59 participants were included in the present analysis. The mean age of the participants was 59.2 ± 5.1 years. 62.7% ( n = 37) were males. A negative, moderate, statistically significant correlation was observed between the rate-pressure product and mean RR(ρ = -0.61; p < 0.001). A positive, strong, statistically significant correlation was observed between the rate-pressure product and mean HR (ρ = 0.70; p < 0.001). The multiple regression analysis demonstrated that RMSSD was a significant negative predictor of RPP (with and without adjusting for medication use). Conclusion The study observed a moderate correlation between the rate-pressure product and mean RR and mean HR, as expected mathematically. The present study also demonstrates RMSSD as a significant negative predictor of resting RPP. Clinically, a raised resting RPP can be a warning sign for altered cardiac autonomic function and, therefore, cardiac autonomic neuropathy. Trial registration The study was registered in the Clinical Trials Registry India (CTRI/2023/11/060077) on 21st November 2023. The study is part of a larger ongoing trial.