Heart rate and heart rate variability in acute coronary heart disease

The parameters of cardiac autonomic function, heart period length and heart period length variability were investigated in 70 patients, 50 males and 20 females, mean age 54.8 +/- 9.6 years, admitted to coronary care unit. There were 15 unstable angina patients, 21 anterior wall infarction patients, 20 posterior wall infarction patients, and 14 non-Q-wave infarction patients, who survived to discharge. Heart period length and heart period length variability for each patient were manually measured on the basis of 30 consecutive sinus normal-to-normal RR intervals in ECG every 20 minutes during the initial 24 hours of their stay at the coronary care unit and in the third week after admission. For each interval analyzed, the mean duration of RR interval was computed. RR interval variations were expressed as coefficient of variation (CV). On admission, heart rate was significantly slower (848 +/- 173 ms vs. 837 +/- 163 ms) and CV significantly lower (4.8 +/- 4.2 vs. 5.0 +/- 3.4%) than on discharge (p < 0.01). The significant difference in the mean RR interval between anterior wall infarction patients (802 +/- 186 ms) and inferior wall infarction patients (879 +/- 181 ms) recorded on admission disappeared on discharge from hospital (806 +/- 144 vs. 783 +/- 100 ms). CV was lower in acute myocardial infarction patients (4.7 +/- 3.6; 4.1 +/- 3.2) than in unstable angina patients (5.3 +/- 5.6) on admission (p < 0.05). Heart rate variability was greater in anterior wall infarction patients and unstable angina patients (CV = 5.3 +/- 3.1; 5.2 +/- 3.6%) than in posterior wall infarction patients and non-Q-wave infarction patients (CV = 4.7 +/- 3.5; 4.8 +/- 3.6%). The findings showed that different degrees of cardiac sympathovagal activity may occur in acute coronary heart disease patients during the first 24 hours of their stay at coronary care unit and on discharge from hospital.