The effects of inotropic myocardial support on heart rate variability in patients with myocardial infarction complicated by heart failure

Aim. The aim of the study was to elucidate the effects of inotropic myocardial support with Levosimendan on spectral and temporal parameters of heart rate variability (HRV) in patients with myocardial infarction (MI) complicated by heart failure (HF). Material and methods. A total of 153 patients with Q wave-positive MI complicated by heart failure (Killip II-III) aged from 34 to 84 years (mean age of 60 (54; 69) years) were assigned to two comparable groups: Group 1 (n=104) received Levosimendan in addition to standard therapy; Group 2 (n=49) did not receive Levosimendan. Twenty four-hour Holter monitoring with HRV evaluation was performed twice: at day 1 or 2 (before administration of Levosimendan in Group 1) and at day 5 or 6 after MI. Results. Patients of both groups did not differ in the frequency of registration and in the forms of arrhythmias in subacute period of MI. The initial parameters of HRV were comparable in both groups. Significant rank reduction for some temporal (SDNN, r-MSSD, pNN50) and spectral (TP, LF, HF) parameters was observed on day 1 and day 2 of MI in both groups. In subacute period of MI, HRV increased in both groups. However, in the presence of Levosimendan, an improvement in the temporal indexes (SDNN, r-MSSD, and pNN50) was more significant; the power of low frequency (LF) spectrum characterizing sympathetic tone increased; the power of high frequency (HF) spectrum characterizing the effects of parasympathetic tone on heart rate also increased. These data indirectly suggested an abolition of an imbalance in the autonomic nervous system. The number of patients with SDNN index lower than 50 ms, a significant predictor of poor prognosis, decreased by two times in Group 1 and did not change in Group 2. Conclusion. Abolition of autonomic nervous system imbalance and correction of hypersympathicotonia can represent the mechanisms of favorable clinical and, possibly, prognostic effects of Levosimendan in patients with MI complicated by heart failure.