NEW ELECTROPHYSIOLOGIC FEATURES AND CATHETER ABLATION OF ATRIOVENTRICULAR AND ATRIOFASCICULAR ACCESSORY PATHWAYS - EVIDENCE OF DECREMENTAL CONDUCTION AND THE ANATOMIC STRUCTURE OF THE MAHAIM PATHWAY

Catheter Ablation for Mahaim Pathways, Introduction: Several modalitie s of catheter ablation have been proposed to eliminate Mahaim pathway conduction. However, limited research has been reported on the electro physiologic nature of this pathway in its entity. Methods and Results: In seven patients, electrophysiologic study was performed, and radiof requency energy was applied to investigate the electrophysiologic clue s for successful ablation. In all seven patients, the Mahaim pathway w as diagnosed as a right-sided atriofascicular or atrioventricular path way with decremental properties. In two patients, two different kinds of electrograms were recorded through the ablation catheter positioned at the Mahaim pathway location: one was suggestive of conduction over the decremental portion, demonstrating a dulled potential; and the ot her of nondecremental conduction, demonstrating a spiked potential. Al l but one of the Mahaim pathways were eliminated successfully at the a trial origin where the spiked Mahaim potential was recorded. Radiofreq uency energy application was performed at the slow potential site resu lting in failure to eliminate the conduction over the Mahaim pathway. Conduction block at the site between the slow and fast potential recor ding sites was provoked by intravenous administration of adenosine, co ncomitant with a decrease in the amplitude of the Mahaim potential. In one patient, the clinical arrhythmia was a sustained monomorphic vent ricular tachycardia originating from the ventricular end of the Mahaim fiber. Conclusion: The identification of Mahaim spiked potentials may be the optimal method to permit their successful ablation. Detailed e lectrophysiologic assessment is indispensable for successful ablation of tachycardias associated with Mahaim fibers because tachycardias una ssociated with Mahaim fibers can occur despite complete elimination of the Mahaim fiber.