Analysis of Local Electrogram Characteristics Correlated with Successful Radiofrequency Catheter Ablation of Accessory Atrioventricular Pathways

Due to the limited myocardial lesions produced by radiofrequency current, the ablation of accessory pathways (AP) requires precise localization of such connections. The purpose of this study was to ascertain ivhich characteristicfs) of the local bipolar electrogram, recorded from the ablation and adjacent electrode immediately prior to the application of radio/requency current, correlated with precision in localization adequate to permit AP ablation. Signal analysis was performed for 326 sets of electrograms preceding the attempted ablation of 107 APs in 100 consecutive patients. For 80 antegrade APs, the following variables were evaluated: (1) the presence or absence of an AP potential; (2) the local atrial‐AP interval; (3) the local atrioventricular (AV) interval; and (4) the relationship between the onset of local ventricular depolarization and onset of delta wave of the surface electrocardiogram. For the 27 concealed APs, the following characteristics were evaluated; (1) the presence or absence of an AP potential; and (2) the local VA interval during reciprocating tachycardia or ventricular pacing. Results: Antegrade APs: By statistical analysis, the best correlate of successful ablation of an antegrade AP was a local AV interval < 40 msec (positive predictive value = 94%; 95% confidence intervals (CI) = 81%–100%), Local AV intervals ≤ 50 msec preceded 88% of successful AP ablations, compared to only 8% of failed radiofrequency current applications. The positive predictive value of the other variables were: presence of an AP potential: 35% (95% CI = 27%–40%); local atrial‐AP intervals < 40 msec: 54% (95% CI = 43%‐66%); and local ventricular depolarization preceding onset of the delta wave 43% (95% CI = 34%‐52%). For concealed APs, the positive predictive value of a VA interval < 60 msec was 71% (95% CI = 48%–88%); the positive predictive value for the presence of an AP potential was 58% (95% CI = 32%–81%). Conclusions: No single electrogram characteristic had a positive predictive value and a sensitivity > 90% for AP localization adequate for radiofrequency current ablation. For antegrade APs, the best correlate of adequate localization was a local AV interval < 40 msec; as a corollary, radiofrequency current applications at sites where the local AV was > 60 msec, were unlikely to be effective. Objective criteria for the localization of concealed APs were less certain. Electrogram analysis, as a guide to AP localization and ablation, requires careful analysis of multiple variables, with analysis of the local AV interval a salient objective factor.