Effects of Revascularization on Cardiac Autonomic Neuropathy in Type 2 Diabetes Mellitus Patients With Chronic Stable Angina

Background: Type 2 diabetes mellitus (T2DM) leads to cardiac autonomic neuropathy (CAN), affecting blood flow and heart rate regulation eventually causing chronic stable angina (CSA). Percutaneous coronary intervention (PCI) can correct autonomic dysfunctions and improve myocardial perfusion. This study aimed to assess CAN using heart rate variability (HRV) and cardiovascular reflex tests in T2DM patients with CSA before and after PCI. Material and methods: From cardiology outpatient clinics, 30 patients with T2DM with CSA were recruited. Before and after PCI, the following HRV parameters like low frequency (LF), high frequency (HF), LF:HF ratio, total power (TP), square root of mean square differences of successive R-R intervals (RMSSD), standard deviation of normal R-R intervals (SDNN), and percentage of adjacent NN intervals that differ from each other by more than 50 seconds (pNN50) were measured for every patient. Cardiovascular reflex tests, including the deep breathing test, the isometric handgrip test, the 30:15 ratio, the Valsalva ratio, and the lying-to-standing test (LST), were performed on the patients both before and after PCI. SPSS version 21.0 (IBM Corp., Armonk, NY), a licensed statistical program, was used to compile and analyze the data. Results: When compared to the pre-PCI group, 30 patients with T2DM with CSA, age range between 45 and 70 years, both genders demonstrated a significant increase in post-PCI HRV frequency domain parameters, such as LF (239.52±67.21 ms2 vs. 307.62±74.17 ms2) and HF (249±25.21 ms2 vs. 379.67±76.55 ms2). The time domain parameters showed a significant increase in post-PCI values compared to pre-PCI values. These included RMSSD (33.97±3.96 ms vs. 8.005±3.25 ms), SDNN (41.4±9.78 vs. 31.74±7.04ms), NN50 (13.241±3.07 vs. 5.20±6.63), and TP (1130.08±320.10 ms2 vs. 754.54±96.93 ms2). In cardiovascular reflex tests, pre-PCI groups had significantly lower delta HR (DBT) (10.47±1.76 bpm vs. 14.20±2.09), E:I ratio (DBT) (1.14±0.042 vs. 1.20±0.026), and Valsalva ratio (1.10±0.071 vs. 1.22±0.084) than post-PCI groups. The pre-PCI group showed a substantial decrease in both the systolic blood pressure (LST) (-6.13±4.85 mmHg vs. -1.01±3.63 mmHg) and the 30:15 ratio (1.13±0.074 vs. 1.09±0.067) when compared to the post-PCI group. The handgrip test (18.73±4.31 mmHg vs. 15.31±4.27 mmHg) did not yield statistically significant results. Conclusions: Before PCI, T2DM patients with CSA experienced autonomic dysfunction, but after revascularization, their functions improved by reestablishing basal cardiac autonomic tone and autonomic reactivity. HRV and cardiovascular reflex tests are useful noninvasive tools for assessing CAN and stratifying a prospective risk factor for estimating the morbidity and death from cardiovascular illnesses in T2DM with CSA.