RADIOFREQUENCY CATHETER ABLATION OF MAHAIM TACHYCARDIA BY TARGETING MAHAIM POTENTIALS AT THE TRICUSPID ANNULUS

Background-Reentrant associated with Mahaim pathways are rare but pote ntially troublesome. Various electrophysiological substrates have been postulated and catheter ablation at several sites has been described. Objective-To assess the efficacy and feasibility of targeting discret e Mahaim potentials recorded on the tricuspid annulus for the delivery of radiofrequency energy in the treatment of Mahaim tachycardia. Pati ents-21 patients out of a consecutive series of 579 patients referred to one of three tertiary centres for catheter ablation of accessory pa thways causing tachycardia. All had symptoms and presented with tachyc ardia of left bundle branch block configuration or had this induced at electrophysiological study. In all cases, the tachycardia was antidro mic with anterograde conduction over a Mahaim pathway. Results-6 patie nts had additional tachycardia substrates (4 had accessory atrioventri cular connections and 2 had dual atrioventricular nodal pathways and a trioventricular nodal reentry). After ablation of the additional pathw ays, Mahaim potentials were identified in 16 (76%) associated with ear ly activation of the distal right bundle branch and radiofrequency ene rgy at this site on the tricuspid annulus abolished Mahaim conduction in all 16 cases. In 2 patients there was early ventricular activation at the annulus without a Mahaim potential but radiofrequency energy ab olished preexcitation. In the remaining patients no potential could be found (1 patient), no tachycardia could be induced after ablation of an additional pathway (1 patient), or no Mahaim conduction was evident during the study (1 patient). During follow up (1-29 months (median 9 months)) all but 1 patient remained symptom free without medication. Conclusions-Additional accessory pathways seem to be common in patient s with Mahaim tachycardias. The identification of Mahaim potentials at the tricuspid annulus confirms that most of these pathways are in the right free wall and permits their successful ablation and the aboliti on of associated tachycardia.