ELECTROGRAMS FOR IDENTIFICATION OF THE ATRIAL ABLATION SITE DURING CATHETER ABLATION OF ACCESSORY PATHWAYS

Background: Catheter ablation of accessory pathways using radiofrequen cy current has been shown to be effective in patients with Wolff-Parki nson-White syndrome, by using either the ventricular or atrial approac h. However, the unipolar electrogram criteria for identifying a succes sful ablation at the atrial site are not well established. Methods and Results: One hundred patients with Wolff-Parkinson-White were treated by delivering radiofrequency energy at the atrial site. Attempts were considered successful when ablation (disappearance of the delta wave) occurred in < 10 seconds. In eight patients with concealed pathway th e accessory pathway location was obtained by measuring the shortest V- A interval either during ventricular pacing or spontaneous or induced reciprocating tachycardia. In 92 patients both atrioventricular valve annuli were mapped during sinus rhythm, in order to identify the acces sory pathway (K) potential before starting the ablation procedure. Whe n a stable filtered (30-250 Hz) ''unipolar'' electrogram was recorded, the following time intervals were measured: (1) from the onset of the atrial to the onset of the K potential (A-K); (2) from the onset of t he delta wave to the onset of the K potential (delta-K); and (3) from the onset of the K potential to the onset of the ventricular deflectio n (K-lr). During unsuccessful Versus successful attempts, A-K (51 +/- 11 ms vs 28 +/- 8 ms, P < 0.0001 for left pathways [LPs]; and 44 +/- 8 ms vs 31 +/- 8 ms, P < 0.02 for right pathways [RPs]) and delta-K int ervals (2 +/- 9 ms vs -18 +/- 10 ms, P < 0.0001 for LPs; and 13 +/- 7 ms vs 5 +/- 8 ms, P < 0.02 ms for RPs) were significantly longer. Conc lusions: Short A-K interval (< 40 ms), and a negative delta-K interval recorded from the catheter positioned in the atrium are strong predic tors of successful ablation of LPs and RPs. Therefore, the identificat ion of the K potential appears to be of paramount importance for posit ioning of the ablation catheter, followed by analysis of A-K and delta -K unipolar electrogram intervals. However, it appears that the mere r ecording of K potential is not, per se, predictive of successful outco me, but rather the A-K and delta-K interval.