Abstract
The diurnal and day-to-day variation in the frequency of ventricular premature contraction (VPC) were observed in 60 cases. Observation was made by Holter 24-hour continuous recording electrocardiograms on two occasions at an interval of approximately 9 days. Two distinct groups emerged; a high-frequency group (35 patients, 7200 contractions or more per day) and a low-frequency group (25patients, less than7200contractions per day).
The following results were obtained:
1) No significant differences in clinical backgrounds including age, sex or underlying diseases were found between two groups.
2) The coefficient of correlation between the number of VPCs per day in both Holter recordings, a higher value was obtained in the high-frequency group than in the low-frequency group(r=0.780 as against r=0.471).
3) VPCs in the high-frequency group tended to occur continuously throughout the 24-hour period in both recordings, while those in the low-frequency group appeared predominantly in the daytime.
4) There were significant correlations between the coefficient of variation, as an index of the magnitude of diurnal fluctuation, and the number of VPCs per day(r=-0.694 in the first recording and r=-0.646in the second recording). The coefficient of variation was significantly larger in the low-frequency group than in the high-frequency one.
5) The incidence of multifocal VPC was not significantly different between two groups, and reproducibility in both recordings was92.3%in the high-frequency group and73.3% in the low-frequency group.
6) Although the incidence of couplet VPC was significantly higher in the high-frequency group than in the low-frequency group, reproducibility was similar in both groups(87.0% as against83.3%, respectively).
7) The incidence of ventricular tachycardia was 29% in the high-frequency group and 8% in the low-frequency group, and reproducibility was 81.8% in the high-frequency group and 100% in the low-frequency group.
8) When the cases were divided into 4 groups according to the number of VPCs per day(28800 or more, 28800-7200, 7200-3600 and 3600 or less), the 95% confidence limits of day-to-day variation in the number of VPCs were 26.2, 51.9, 61.2 and 90.1%, respectively.
The 95% confidence limits were found to contribute to the evaluation of the efficacy of antiarrhythmic drugs against VPC.
