[Spontaneous variability of ventricular extrasystole in chronic Chagas cardiopathy]

To study the spontaneous variability of single (VPCs) and coupled (CVPCs) in patients with chronic Chagas' disease (CCD).

Twenty patients with CCD, 14 male, in class I and II NYHA, with frequent VPCs and VCPCs, free of drug therapy were studied. 21 hour Holter monitoring was done for 4 subsequent days. The data analysis assessed the variation in the frequency of VPCs and CVPCs between patients, seven hour periods one hour periods in a hierarchical model by a Poisson process.

a) the frequency of VPCs follows a circadian rhythm, closely related to the hourly variations of the mean heart rate; b) disregarding the heart rate influence on the variability of the ventricular arrhythmia, its behavior was at random and unpredictable; c) the minimal percentual reduction in VPCs/h that discriminated between antiarrhythmic effect and spontaneous between antiarrhythmic effect and spontaneous between antiarrhythmic effect and spontaneous variability was 121.86% for seven-hour, 58.42% for 21-hour and 38.45% for 42-hour electrocardiographic monitoring periods; d) the same approach for the VCPCs revealed values of 133.6%, 63.21% and 41.3% respectively.

The large variability of ventricular arrhythmia in CCD during a 24 hour period makes necessary observations always longer. The minimal percentual reduction in VPCs/h that discriminated between antiarrhythmic effect and spontaneous variability might be 58.42% for two 21-hour electrocardiography monitoring periods.