REASONS FOR PROLONGED OR FAILED ATTEMPTS AT RADIOFREQUENCY CATHETER ABLATION OF ACCESSORY PATHWAYS

Objectives. The purpose of this study was to categorize the reasons fo r a prolonged or failed procedure in a series of patients undergoing c atheter ablation of an accessory pathway. Background. Radiofrequency a blation of accessory pathways at times requires a lengthy procedure or a second ablation session, or both, and no prior studies have systema tically investigated the reasons for this. Methods. In a consecutive s eries of 619 patients undergoing catheter ablation of an accessory pat hway, the mean ablation time +/- SD was 68 +/- 64 min. The subjects of this study were 14 patients who had an ablation time > 2 SD greater t han the mean (> 196 min) and 51 patients who required a second ablatio n session for a successful outcome. The accessory pathway in the 65 pa tients in this study was located in the right free wall in 19 patients (29%), septum in 14 (22%) and left free wall in 32 (49%). Results. Th e primary reasons for a lengthy or failed ablation attempt were 1) ina bility to position the ablation catheter at the effective target site (16 patients, 25%); 2) instability of the ablation catheter or inadequ ate tissue contact at the target site, or both (15 patients, 23%); 3) mapping error due to an oblique course of the accessory pathway (7 pat ients, 11%); 4) failure to recognize a posteroseptal accessory pathway as being left-sided instead of right sided (4 patients, 6%); 5) other errors in accessory pathway localization (6 patients, 9%); 6) epicard ial location of the accessory pathway (5 patients, 8%); 7) recurrent a trial fibrillation (2 patients, 3%); 8) occurrence of a complication ( 2 patients, 3%); 9) unusual right-sided accessory pathway that inserte d in the anterior right ventricle, 2 cm away from the lateral tricuspi d annulus (1 patient, 1.5%); and 10) unexplained factors (7 patients, 11%). The most common effective strategies employed to achieve a succe ssful outcome in these patients were 1) substitution of a more experie nced operator; 2) use of ablation catheters of varying configurations; 3) switching from a retrograde aortic to a transseptal approach; 4) s witching from an inferior to a superior vena caval approach; 5) use of a 60-cm guiding sheath; 6) detailed mapping of the atrial or ventricu lar insertion of the accessory pathway; and 7) searching within the co ronary sinus for a presumed accessory pathway potential. Conclusions. A lengthy or failed attempt at catheter ablation of an accessory pathw ay may be due to a variety of reasons, the most common of which are pr oblems related to some aspect of catheter manipulation and errors in a ccessory pathway localization. Knowledge of the most common reasons fo r a lengthy or ineffective procedure may facilitate successful outcome of accessory pathway ablation.