Study of heart rate variability dynamic changes in patients with myocarditis

Abstract

Aim. To study dynamic changes of heart rate variability, structural and functional changes in myocardium in patients with myocarditis. Materials and Methods. We examined 42 patients with acute myocarditis confirmed by cardiac magnetic-resonance imaging. Patients were devided into two groups: 22 patients were included in the 1st group, in which we observed the recovery of left ventricular ejection fraction (>40%) in 6 months after the disease onset. The 2nd group consisted of 20 patients who did not undergo restoration of myocardial contractile function - left ventricular ejection fraction Ј 40% after 6 months of observation. The following indicators of Holter monitoring of the electrocardiogram were studied: the percentage of ventricular extrasystoles, presence of non-sustained ventricular tachycardia and parameters of heart rate variability: the mean square deviation of the intervals between ventricular complexes, square root of the mean square of the difference in interval between ventricular complexes, the ratio of the spectrum of high frequency waves to the power of low frequency waves intervals between the ventricular complexes. By the use of 2D-echocardiography the end-diastolic volume index and the ejection fraction of left ventricle were measured, the speckle-tracking method of the echocardiography measured the values of longitudinal global systolic strain, circumferential global systolic strain and radial global systolic strain. Results and Discussion. The frequency and spectral parameters of heart rate variability in the 1st group were significantly lower in comparison with the 2nd group. In addition in both groups after 6 months, there was an increase in the main parameters of heart rate variability - square deviation of the intervals between the ventricular complexes and the ratio of high frequency/low frequency waves, but in the 2nd group these indicators were on 16.1% and 21.3% lower respectively. According to the results of speckle-tracking echocardiography during the 6 months of observation in the 1st group we observed a significant increase of longitudinal strain on 31.8% (P<0,02) and circumferential strain on 28.9% (P<0,05), at the same time, no significant changes were documented in the 2nd group. By the use correlation analysis in the 2nd group we established inverse correlation between the value of square deviation of the intervals between the ventricular complexes on the 1st month after the onset of the disease and the presence of unstable ventricular tachycardia after 6 months of observation (r=-0,52; P<0,02). Conclusions. In patients who didn't have a significant increase in the parameters of the global and segmental contractile function of the myocardium during the 6 months a decrease in the baseline heart rate variability indicates a marked violation of the autonomic regulation of the cardiac rhythm and the tendency to development of arrhythmias. The decrease in the frequency and spectral values of heart rate variability on the background of persistent systolic left ventricular dysfunction in patients with myocarditis is associated with the presence of ventricular arrhythmias and persistence of unstable ventricular tachycardia after 6 months.

Keywords

• myocarditis, cardiac rhythm variability, heart failure, cardiac arrhythmias, fibrosis, holter electrocardiogram monitoring