RADIOFREQUENCY CATHETER ABLATION OF MAHAIM FIBERS AT THE TRICUSPID ANNULUS

Background. The purpose of this study was to test the feasibility of radiofrequency catheter ablation of Mahaim fibers at the tricuspid annulus. Methods and Results. Four patients who fulfilled criteria for having Mahaim fibers and preexcited reciprocating tachycardia underwent radiofrequency catheter ablation. Three patients had atriofascicular connections, and one patient had an atrioventricular connection. The mean age was 27 years (age range, 11-48 years). All patients had highly symptomatic tachycardias, producing syncope in one patient and presyncope in the remaining three patients. Symptoms were present for a mean of 13 years (range, 4-23 years). All pathways conducted only anterogradely, and preexcitation resulted in a left bundle branch block QRS morphology. Adenosine caused block in the accessory pathway in the three patients in whom it was tested. The stimulus to delta interval increased by 75 msec (range, 35-90 msec) during rapid atrial pacing. The atrial insertion of the Mahaim fiber was in the right lateral atrium in one patient, right posterolateral atrium in two patients, and right posterior atrium in one patient. The ventricular insertion was in the distal right bundle branch in three patients and in the posterolateral right ventricle near the tricuspid annulus in the patient with an atrioventricular connection. Stimulus to delta wave mapping was used to help localize the atrial insertion of the atriofascicular connections. A mean of 15 radiofrequency pulses (range, 10-19 pulses) delivered to the tricuspid annulus in the posterior to lateral regions eliminated accessory pathway conduction in all patients. No complications occurred. Tachycardia did not recur during a mean follow-up of 8 months (range, 2-15 months). Conclusions. Radiofrequency current applied to the tricuspid annulus can safely eliminate tachycardia in patients with Mahaim fibers.