Patterns of heart rate variability in patients with atrial fibrillation and arterial hypertension according to the presence of type 2 diabetes mellitus

Aim. To assess the patterns and circadian characteristics of heart rate variability (HRV) as a marker of autonomic dysfunction in patients with atrial fibrillation (AF) and arterial hypertension (AH) depending on the presence of type 2 diabetes mellitus (T2DM), and to determine their clinical associations. Materials and methods. A total of 42 patients with AF were examined: Group 1 (main group) included 21 patients with AF, AH, and T2DM; Group 2 (comparison group) comprised 21 patients with AF and AH without T2DM. All patients underwent comprehensive clinical examination including 24-hour ECG monitoring with the assessment of HRV parameters separately for daytime and nighttime periods. Results. In Group 1, persistent AF was observed more frequently than in Group 2 as was higher symptom burden and greater thromboembolic risk. Compared with Group 2, patients in Group 1 demonstrated significantly lower time-domain HRV indices (SDNNi, RMSSD, pNN50), lower HRV TI and TP, higher regulatory stress indices (SI, IVR, VPR), and an elevated LF/HF ratio, collectively indicating a shift in autonomic balance toward sympathetic predominance. The most pronounced inter-group differences were observed during the nighttime period and were characterized by attenuation of day-to-night variation in HRV indices and reduced nocturnal parasympathetic activity. Correlation analysis in Group 1 revealed significant inverse associations between glycemic control and time-domain, spectral and geometric HRV parameters, as well as direct associations with stress regulatory indices. Conclusions. In patients with AF and AH, comorbid T2DM is associated with more pronounced suppression of overall HRV, elevated regulatory stress indices, sympathetic predominance, and reduced parasympathetic activity. These changes exhibit distinct circadian features, being most marked during the nighttime period. Poorer glycemic control is associated with adverse changes in HRV parameters, suggesting the importance of comprehensive assessment of autonomic dysfunction in patients with metabolic comorbidity.