Reproducibility in circadian rhythm of ventricular premature complexes

To evaluate the existence and reproducibility of a circadian rhythm of ventricular premature complexes (VPCs), 38 patients (mean age 57 ± 17 years) with ≥30 VPCs/hour were studied with 24-hour electrocardiogram Holter monitoring. Nineteen patients had coronary artery disease and 19 had structurally normal hearts. A second Holter electrocardiogram was recorded in all patients from 2 to 47 days (mean 11) after the first. Chronobiologic analysis was made by single and mean cosinor methods. A significant and similar circadian rhythm of VPCs was found in the total sample both on the first (mesor 399, acrophase at 15:08, p <0.01) and the second day (mesor 306, acrophase at 14:47, p <0.05), with 2 main peaks, the first in the late morning and the second in the afternoon. However, only 18 patients (47%, group A) had a significant individual circadian rhythm of VPCs on both days, whereas 20 (53%, group B) did not have a significant rhythm in ≥1 day. A high reproducibility of the circadian rhythm of VPCs was found in group A patients, with a difference of 2.1 ± 1.8 hours between the acrophases of the 2 days, whereas this difference was 4.4 ± 3.3 hours in group B patients (p <0.01). Among group A patients, 14 (78%) had a VPC rhythm with acrophase occurring during waking hours, whereas the acrophase of 4 (22%) occurred during the night. The reproducibility of the circadian rhythm of VPCs was not influenced by gender, presence of coronary disease, medical therapy, basal VPC number, or day-to-day variability of VPCs, although group A patients were older than group B patients (p <0.05). The evidence, of a reproducible circadian rhythm of VPCs in a significant number of patients, suggests the possibility of a chronopharmacologic approach to their treatment.