Clinical Correlates of Cardiovascular Autonomic Measures in Patients with Type 2 Diabetes: A Cross-Sectional Study

Background/Objectives: Cardiovascular autonomic dysfunction in type 2 Diabetes Mellitus (T2DM) is heterogeneous, and individual autonomic measures may identify distinct clinical profiles. This study assessed the clinical, neuropathic, metabolic, and vascular correlates of three cardiovascular autonomic measures: the expiratory-to-inspiratory (E:I) R–R interval ratio, orthostatic blood pressure response, and corrected QT interval (QTc). Methods: This secondary cross-sectional analysis included 109 patients with T2DM from a previously characterized cohort. Cardiovagal function was assessed using the E:I R–R interval ratio during deep breathing. Orthostatic hypotension (OH) was defined according to systolic and diastolic blood pressure changes after standing, while QTc was calculated using Bazett’s formula. Peripheral neuropathy was evaluated using the Michigan Neuropathy Screening Instrument (MNSI) and Toronto Clinical Neuropathy Score (TCNS), and peripheral vascular status using the ankle–brachial pressure index (ABI). Group comparisons, chi-square or Fisher exact tests as appropriate, odds ratios (OR) with 95% confidence intervals (CI), Spearman correlation analyses, and multivariable linear regression analyses were performed. Exploratory families of comparisons and correlations were controlled using the Benjamini–Hochberg false discovery rate procedure. Results: A pathological E:I R–R interval ratio was identified in 90 patients (82.6%), prolonged QTc in 23 (21.1%), and orthostatic hypotension in 40 (36.7%). Categorical OH was not associated with the evaluated clinical, neuropathic, or vascular parameters. In contrast, continuous systolic blood pressure change after standing (ΔSBP) was independently associated with peripheral neuropathy severity, assessed using the MNSI and TCNS. The nominal univariable association between ΔSBP and HbA1c did not remain significant after false-discovery-rate correction or multivariable adjustment. QTc prolongation showed no consistent association pattern with the other evaluated autonomic-related measures. Conclusions: The evaluated cardiovascular autonomic measures showed partially distinct cross-sectional association patterns in patients with T2DM. Continuous ΔSBP was independently associated with peripheral neuropathy severity, whereas categorical orthostatic hypotension showed no significant associations. The E:I R–R interval ratio and QTc prolongation showed limited overlap with the other evaluated measures. These findings are hypothesis-generating and do not establish the diagnostic utility of individual measures for cardiovascular autonomic neuropathy.