RR VARIABILITY IN HEALTHY, MIDDLE-AGED PERSONS COMPARED WITH PATIENTSWITH CHRONIC CORONARY HEART-DISEASE OR RECENT ACUTE MYOCARDIAL-INFARCTION

Background The purpose of this investigation was to establish normal v alues of RR variability for middle-aged persons and compare them with values found in patients early and late after myocardial infarction. W e hypothesized that presence or absence of coronary heart disease, age , and sex (in this order of importance) are all correlated with RR var iability. Methods and Results To determine normal values for RR variab ility in middle-aged persons, we recruited a sample of 274 healthy per sons 40 to 69 years old. To determine the effect of acute myocardial i nfarction RR variability, we compared measurements of RR variability m ade 2 weeks after myocardial infarction (n=684) with measurements made on age- and sex-matched middle-aged subjects with no history of cardi ovascular disease (n=274). To determine the extent of recovery of RR v ariability after myocardial infarction, we compared measurements of RR variability made in the group of healthy middle-aged persons with mea surements made in 278 patients studied 1 year after myocardial infarct ion. We performed power spectral analyses on continuous 24-hour ECG re cordings to quantify total power, ultralow-frequency (ULF) power, very -low-frequency (VLF) power, low-frequency (LF) power, high-frequency ( HF) power, and the ratio of LF to HF (LF/HF) power. Time-domain measur es also were calculated. All measures of RR variability were significa ntly and substantially lower in patients with chronic or subacute coro nary heart disease than in healthy subjects. The difference from norma l values was much greater 2 weeks after myocardial infarction than 1 y ear after infarction, but the fractional distribution of total power i nto its four component bands was similar for the three groups. In heal thy subjects, ULF power did not change significantly with age; VLF, LF , and HF power decreased significantly as age increased. Patients with chronic coronary heart disease showed little relation between power s pectral measures of RR variability and age. Patients with a recent myo cardial infarction showed a strong inverse relation between VLF, LF, a nd HF power and age and a weak inverse relation between ULF power and age. ULF power best separates the healthy group from either of the two coronary heart disease groups. Differences in RR variability between men and women were small and inconsistent among the three groups. Conc lusions All measures of RR variability were significantly and substant ially higher in healthy subjects than in patients with chronic or suba cute coronary heart disease. The difference between healthy middle-age d persons and these with coronary heart disease was much greater 2 wee ks after myocardial infarction than 1 year after infarction, but the f ractional distribution of total power into its four component bands wa s similar for the healthy group and the two coronary heart disease gro ups. Values of RR variability previously reported to predict death in patients with known chronic coronary heart disease are rarely (approxi mate to 1%) found in healthy middle-aged individuals. Thus, when measu res of RR variability are used to screen groups of middle-aged persons to identify individuals who have substantial risk of coronary deaths or arrhythmic events, misclassification of healthy middle-aged persons should be rare.