[An analysis of the circadian rhythm of the heart rate and arrhythmias in healthy elderly subjects]

Abstract

The incidence of asymptomatic arrhythmia detected by Holter monitor in the normal aged population is high. Nevertheless, there are few studies in the literature about the existence and characteristics of their circadian rhythm (CR). The aim of this study, is to determine the presence of CR of the heart rate (HR), supraventricular and ventricular extrasystoles (SVE, VE), atrial tachycardias (AT) and ventricular complex tachycardias (VCT) in the normal aged population. We studied 120 subjects, older than 70 years of age, belonging to a pensioner club, without apparent cardiovascular disease by history, physical, ECG, Chest X-Ray and echocardiography. All the patients had a 24 hours Holter monitor. 42 patients whose recording showed more than 50 SVE and/or more than 50 VE were included in the study. To study the CR the cosinor method was used. In the simple analysis, the HR had significant CR in 40 subjects (95.2%), the SVE in 18 out of 29 (62.1%) and the VE in 16 out of 26 (61.5%). The global analysis showed significant CR for the HR, with an acrophase at 15:47 hours (confidence limits at 95% between 14:45 and 15:42 hours) and for the VE, (acrophase: 15:35 hours, confidence limits between 11:53 and 19:05 hours). There was not significant CR for the SVE because the wide dispersion of the acrophases between the subjects. The AT had significant CR but no the VCT. We conclude that the majority of the aged normal subjects with frequent ectopy had significant CR for the HR and extrasystoles. The VE follow a CR similar to the frequency, suggesting a common modulation of the autonomic nervous system. The SVE variation follow a different CR.