EVOLUTION OF CHANGES IN THE VENTRICULAR RHYTHM DURING PAROXYSMAL ATRIAL-FIBRILLATION

Changes in the RR interval within episodes of paroxysmal atrial fibril lation. (PAF) have not been fully characterized. A database of 177 24- hour Holter recordings were created from patients with PAF in the CRAF T studies. PAF episodes of greater than or equal to 1 minute duration containing less than or equal to 20% noise and preceded by greater tha n or equal to 1 minute of sinus rhythm with I 20% noise were selected. Sections of each AF episode containing 10 and 25 RR intervals were id entified at the onset, middle, and termination of each episode. Descri ptive characteristics (mean, SD, and RMSSD of RR intervals) were calcu lated within each section, and compared using a nonparametric, paired Wilcoxon test. In 25 patients (17 men, 60.6 +/- 12.2 years old), 231 e pisodes from 44 recordings met the selection criteria. The mean RR int erval increased slightly between the onset and mid-portion of AF episo des (565.9 +/- 128.3 vs 580.3 +/- 144.7 ms, P < 0.001). The RR interva l at the termination of AF was significantly greater than that at the start (627.1 +/- 156.1 vs 565.9 ms, P < 10-11) or mid-portion. (627.1 +/- 156.1 vs 580.3 +/- 144.7 ms, P < 10-13). SD of the RR interval inc reased significantly between onset and mid-portion (111.1 +/- 60.2 vs 118.2 +/- 66.7 ms, P < 0.001) and more substantially between mid-porti on and termination (118.2 +/- 66.7 vs 201.8 +/- 93.7 ms, P < 10-21). D uring paroxysms of AF, the mean RR interval and the variability of RR intervals increases. Termination of a paroxysm is preceded by a marked increase in RR interval variability.