Heart rate variability in post-infarction patients with heart failure

Abstract

During the stratification of risk for patients after myocardial infarction (MI), assessment of autonomic imbalance plays an important role. Heart rate variability (HRV) after MI has important prognostic value regarding the prediction of overall mortality of patients, identify patients at risk for symptomatic sustained ventricular tachycardia, evaluation of the clinical course of heart failure and its prognosis. Purpose. Set features of HRV in patients with recurrent myocardial infarction according to Halter-ECG monitoring. Materials and methods. The study involved 160 patients with recurrent myocardial infarction with heart failure who have made a major group and 15 patients without recurrent myocardial infarction with heart failure (control group). Investigation of heart rate variability was performed on a 5-minute recording with the help of CARDIOLAB the product of the company HAI-MEDICA (Kharkiv, Ukraine). Results and discussion. The analysis of HRV in examined patients, depending on the amount of carried over MI in history showed that at the time of hospitalization is a decrease in autonomic tone with predominance of the sympathetic nervous system. In particular, the LF/HF ratio in the normal sense of (1.65±0.2) st. un. in patients of the main group with recurrent MI was (2.45±0.9) st. un. (p<0.0001), and the tertiary (3.5±0.25) st. un. (p<0.0001). Patients in the control group had LF/HF ratio (1.48±0.08) st. un. (p<0.05). Concerning the HRV depending on the stage of heart failure, it became clear that the SDNN is held equally by heart failure II and III stages. Index LF/HF remained increased in patients with heart failure of both stages, indicating the superiority of sympathetic influences on the heart. HRV depending on the duration of heart failure showed that the values of SDNN wasn`t significantly changed and was reduced. Index LF/HF was steadily increased with the duration of HF >6 years (2.89±0.18) st. un. in the study group (p<0.0001) versus (1.65±0.2) st.n. in healthy individuals. During the systolic and diastolic dysfunction, key changes in parameters of HRV were monosemantic: SDNN-reduced, and LF/HF-enhanced. Types of diastolic dysfunction did not significantly affect the HRV. Conclusions. So, in all patients with recurrent myocardial infarction, regardless of the number of carried over MI, stage or duration of heart failure and type of dysfunction of the left ventricle, prevailed sympathetic effects on the heart, according to the analysis of heart rate variability. All treatment methods resulted in a significant improvement in overall heart rate variability, as evidenced by a downward trend in LF/HF.