[Physiological limits of variations in heart rate measured by the Holter method in 134 normal subjects]

Ambulatory 24 hour electrocardiography by the Holter method was carried out in 134 normal subjects (59 men, 75 women, mean age: 42.5 +/- 14 years). The average heart rate over 24 hours was 75 +/- 9 bpm, 82 +/- 10 bpm during the daytime and 64 +/- 8 bpm at night. Maximal and minimal momentary variations (over 5 minutes) were small during the night (+23% and -7%) and greater during the daytime (+47% and -16%). The heart rate slowed progressively over a two hour period before going to bed an increased progressively over a three hour period, reaching a peak and then slightly falling before getting up. The average heart rates of women were faster than in men (+5 bpm). The average heart rate fell with age from 30 years onwards (-0.4 bpm per year). Tobacco consumption did not seem to affect the heart rate. Supraventricular extrasystoles were observed in 68% of subjects during the day, and in 50% during the night; ventricular extrasystoles occurred in 42% of subjects by day and in 23% by night. Only 22% of subjects had no extrasystolic activity. Tobacco consumption and sex were unrelated to the incidence and frequency of extrasystoles. On the other hand, the incidence and frequency of extrasystoles were very significantly related to age.