Differentiation between aberrant ventricular conduction and ventricular ectopy in atrial fibrillation using RR interval scattergram

Background. Differentiation between aberrant ventricular conduction and ventricular ectopy during atrial fibrillation (AF) is of etiologic, prognostic, and therapeutic importance. We developed a noninvasive technique to diagnose aberrant ventricular conduction and ventricular ectopy in AF. Methods and Results. We studied the Holter ECGs of 34 patients with paroxysmal AF and 62 patients with chronic AF. In all the patients, frequent wide QRS complexes were observed, and 32 patients were shown by electrophysiological examination to have ventricular ectopies or aberrant ventricular conductions. We obtained the RR interval scattergrams by plotting sequential pairs of RR intervals. Each point has the (n)th RR interval as its x value and the (n+1)th RR interval as its y value. The irregularity of the RR intervals in AF resulted in widely scattered points delineated by the envelope along the axes. The y value of the envelope along the x axis indicates the shortest coupling interval to the preceding RR interval. Therefore, this curve defines the functional refractory period of atrioventricular conduction. The scattergram of the RR interval pairs immediately preceding the aberrant conduction (coupling points of aberrant conduction) specifically distributed along the envelope. In contrast, the coupling points of ventricular ectopies showed different distributions that had no relation to the envelope. That is, it included three typical patterns, ie, linear distribution below the envelope, linear distribution partially overlapped in the area of normal AF conduction, and chaotic distribution in the AF area. None of the scattergrams of ventricular ectopies showed curvilinear distribution along the envelope as aberrant conduction did. The specific distribution of the aberrant conduction on the RR interval scattergram suggested that aberrant conduction in AF could result from the difference of refractory periods between the AV node and bundle branch block. Conclusions. We conclude that the RR interval scattergram makes it possible to differentiate between aberrant ventricular conduction and ventricular ectopy in atrial fibrillation, and thus, it is a useful noninvasive clinical tool.