The aim – to study heart rate variability (HRV), structural and functional heart state in patients with myocarditis and dilated cardiomyopathy (DCM).
Material and methods. We examined 56 patients: 34 with clinically suspected myocarditis (1st group) and 22 with DCM (2nd group), the average age 38.2±2.9 and 43.1±3.4 years, respectively. All patients had left ventricular systolic dysfunction – ejection fraction ≤ 45 %. Control group included 20 healthy individuals matched by age. By the use of 24-hour ECG monitoring we studied parameters of HRV: standard deviation of normal RR intervals (SDNN), root-mean-square successive difference (RMSSD), low frequency / high frequency power ratio (LF/HF), as well as frequency of ventricular extrasystoles (VE) and incidence of non-sustained ventricular tachycardia (NSVT). All patients underwent echoСG and cardiac MRI for verification of the diagnosis.
Results. In patients of the 1st group hyperemia and edema were detected in 58.8 and 38.2 % of cases respectively, while late enhancement – in 52.9 %. In the 2nd group we observed only late enhancement in multiple segments of myocardium in 90.9 % of the patients that was a distinctive feature of diffuse myocardial fibrosis. Patients of the 2nd group compared to the 1st were characterized by the lower values of SDNN – 82.5±8.9 vs 101.9±7.2 ms (P<0.01), RMSSD – 29.7±4.4 vs 41.6±4.8 ms (P<0.02) and LF/HF ratio – 0.91±0.07 vs 1.39±0.08 (P<0.05) respectively. The frequencies of VE and NSVT were higher in the 2nd group in comparison with the 1st – 1.75±0.24 vs 1.11±0.21 % (P<0.01) and 27.3 vs 18.1 % (P<0.01) respectively. MRI revealed edema and/or hyperemia in the 1st and diffuse myocardial fibrosis in the 2nd group. The strong reverse correlation was found in the 2nd group between SDNN, LF/HF ratio and the presence of diffuse myocardial fibrosis – r=–0.72 (P<0.02); r=–0.74 (P<0.01), respectively. In the 2nd group we observed reverse correlation between SDNN and the frequency of VE and presence of NSVT – r=–0.67 (P<0.01); r=–0.56 (P<0.05) respectively, as also between LF/HF ratio and the presence of NSVT – r=–0.80 (P<0.01). Conclusions. In patients with dilated cardiomyopathy compared to myocarditis we established more pronounced impairment of sympathetic and parasympathetic heart rate regulation by the lower values of SDNN and HF/LF ratio as also more frequent ventricular rhythm disorders that was associated with diffuse myocardial fibrosis. Association of HRV impairment and supraventricular rhythm disorders with atrial dimensions was found in both myocarditis and DCM.