Atriofascicular pathways: Where to ablate?

Background: Atriofascicular accessory pathway (AP), often referred to as Mahaim pathway, is an uncommon form of preexcitation. The usual target for ablation is at the site of a high-frequency potential along the tricuspid annulus (TA). We present our observations in mapping and ablation of 29 patients with atriofascicular APs. Methods and Results: Twenty-nine consecutive patients who underwent radiofrequency ablation (RFA) for atriofascicular pathways comprised the series. Demographic factors, clinical features of the tachycardia, ablution site, and results were analyzed. The mean age was 19 8 years; 15 were men. Three patients had Ebstein's anomaly of the tricuspid valve. Four patients had an additional AP and two patients had concomitant typical atrioventricular nodal reentrant tachycardia. RFA was successful in 28 patients (97%); repeat ablation was required in two patients. The site of successful ablation was on the TA at the site of a sharp, high frequency potential in 15 patients (52%). In the remaining 14 patients, a potential was not found along the TA, and ablation was targeted at the ventricular insertion of the AP into the distal right bundle. At the successful ventricular ablation site, local ventricular activation preceded the surface electrocardiogram by 20 +/- 6 ms. Eight of the 14 patients (57%) undergoing ablation in the ventricle, developed right bundle branch block (RBBB). One patient who underwent successful ablation along the TA also manifested RBBB after ablation; however, this patient had Ebstein's anomaly and preexcitation had completely masked the RBBB. The mean procedure and fluoroscopy time was 150 +/- 32 and 35 +/- 12 minutes, respectively. Conclusions: In atriofascicular pathways, an AP potential was found along the TA in only 52% of patients. Ablation at the ventricular insertion site often resulted in RBBB (57%), but the AP was also successfully ablated.