Time course of short-term resting heart rate variability after myocardial infarction

In order to evaluate time course of short term resting heart rate variabili ty (HRV) after acute myocardial infarction 93 patients (59 men) were enroll ed into a prospective study. Q-wave was registered in 71%, infarction was a nterior in 44,1% and thrombolysis was used in 32,2% of patients. Mean of no rmal RR intervals (RRNN), standard deviation of normal 88 intervals (SDNN), very low (VLF, 0,003-0,04 Hz), low (LF; 0,04-0,15 Hz) and high (HF; 0,15-0 ,40 Hz) frequency powers, total power (TP; 0,003-0,40 Hz) as well as LF/HF ratio and normalized LF power were obtained from 10-25 min ECC strips recor ded during supine rest on days 2-4 (median 3), week 3 and in 1 year after M I. At these time points B-blockers received 92,5, 81,7, 71%, clinical signs of heart failure emerged in 5,4, 2,2, and 14%, suffered from angina 21,5, 33,3, 66,6% of patients, respectively There were no recurrent myocardial in farctions during follow-up. Echocardiography at 1 year after MI revealed si gnificant increases of average left ventricular end systolic and diastolic volumes compared with figures obtained in the acute phase. On week 3 after MI increases in RRNN and HRV parameters occurred but sympatho-vagal balance did not change relative to initial study on days 2-4. By the end of 1 year RRNN decreased, SDNN, TP, VLF and LF powers remained unchanged, and unexpe cted decrease of HF power with relative augmentation of sympathetic activit y occurred. These unfavorable changes of HRV at supine rest might have refl ected clinical deterioration in many patients. Subgroup analysis showed tha t augmentation of HRV parameters after 1 year took place only in patients i n highest tertile of heart rate distribution (with mean heart rate >67 beat s/ min) on days 2-4 of MI.