ALTERATIONS IN HEART-RATE-VARIABILITY AND ITS CIRCADIAN-RHYTHM IN HYPERTENSIVE PATIENTS WITH LEFT-VENTRICULAR HYPERTROPHY FREE OF CORONARY-ARTERY DISEASE

Heart rate variability (HRV) and its circadian rhythm were evaluated i n 22 patients with treated hypertension and left ventricular hypertrop hy in whom coronary artery disease was excluded by stress thallium or angiography. By using 24-hour Holter monitoring, HRV and its spectral components were measured. Findings were compared with 11 age-matched n ormal controls. The difference between mean R-R intervals during sleep (11 PM to 7 AM) and while awake (9 AM to 9 PM) (73 +/- 33 vs 263 +/- 63 msec, p < 0.0001) and the mean 24-hour SD of the R-R intervals (55 +/- 6.3 vs 93 +/- 11, p < 0.0001) were lower among the hypertensive pa tients compared with controls. The percentage of difference between su ccessive R-R intervals that exceeded 50 msec, a measure of parasympath etic tone, was also lower among the hypertensive patients (6.8 +/- 7.1 vs 13.6 +/- 8.9, p < 0.002); it increased at night and decreased duri ng the day among the controls, and this circadian rhythm was blunted a mong the patients. Spectral analysis showed that power in the high-fre quency range (0.15 to 0.40 Hz) was lower among the hypertensive patien ts during 21 of 24 hours but that the difference was statistically sig nificant only during 9 hours (p ranging from < 0.05 to 0.009). Power i n the low-frequency range (0.04 to 015 Hz) was lower at night, increas ed in the morning, and higher during the day among controls; this circ adian rhythm was absent among hypertensive patients. Among hypertensiv e patients free of coronary artery disease, HRV is decreased with a pa rtial withdrawal of parasympathetic tone, and the circadian rhythm of sympathetic/parasympathetic tone is altered.