title: An analysis of post-pacing R-R intervals during atrial fibrillation.
abstract: Bursts of ventricular pacing at cycle lengths of 350-260 ms were introduced during atrial fibrillation in nine patients, and the post-pacing R-R intervals were compared to the R-R intervals of spontaneous QRS complexes. In eight of nine patients, the mean post-pacing R-R interval was 126-199 ms longer than the mean spontaneous R-R interval (p less than 0.005). Spontaneous runs of aberrantly conducted supraventricular complexes were recorded during atrial fibrillation in one patient. The mean R-R interval following the runs of aberrantly conducted supraventricular complexes was significantly longer than the mean R-R interval of spontaneous narrow QRS complexes (p less than 0.001), but not significantly different than the mean post-pacing R-R interval. The findings of this study suggest that the R-R interval that follows a wide-complex tachycardia during atrial fibrillation is unlikely to be of value in differentiating ventricular tachycardia from aberrantly conducted supraventricular complexes. Analysis of R-R intervals that follow bursts of ventricular pacing suggests that there is likely to be considerable overlap between the R-R intervals that follow runs of ventricular tachycardia and the spontaneous R-R intervals during atrial fibrillation. Furthermore, even when the post-tachycardia R-R interval clearly exceeds the longest spontaneous R-R interval during atrial fibrillation, this is still of little diagnostic value, because a long pause may occur after either a run of ventricular tachycardia or a run of aberrantly conducted QRS complexes of supraventricular origin.
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013610:Tachycardia / Q000175:diagnosis