Mahaim automatic accelerated rhythm: a marker of successful radiofrequency ablation.

BACKGROUND: Mahaim pathways are characterized by the presence of an accessory pathway potential-the 'M' potential, at the tricuspid annulus. M potential is a very useful guide during radiofrequency ablation of Mahaim pathway. During ablation, an accelerated rhythm with ORS morphology, identical to fully pre-excited QRS complex is observed, and has been labeled as Mahaim automatic rhythm. We analyzed this rhythm during radiofrequency ablation of these pathways. METHODS AND RESULTS: Eighteen patients with Mahaim accessory pathways were taken up for electrophysiology study and radiofrequency ablation. Tricuspid annulus was mapped for 'M' potentials and targeted for ablation. Duration of ablation and number of ablation attempts were guided by Mahaim automatic rhythm during ablation. Mahaim tachycardia was inducible in all. 'M' potentials were recorded in 15/18 patients. Radiofrequency energy was delivered at the site where Mahaim accelerated rhythm was noticed and was continued till abolition of the rhythm. This resulted in long-term success. In 3 patients, M potentials were not recordable, and in them other methods including 3-dimensional electroanatomical mapping was also not successful. CONCLUSIONS: 'M' potential-guided radiofrequency ablation is a useful technique. Presence of Mahaim automatic rhythm and its abolition during ablation is associated with long-term success of the procedure.

Left atrial-coronary sinus dissociation following an attempt at radiofrequency ablation for a left lateral accessory pathway.

Coronary sinus electrograms generally represent the sequence of left atrial activation, and are very helpful in localizing and differentiating left lateral accessory pathway-mediated tachycardia from other supraventricular tachycardias. The activation of the coronary sinus from the left atrium occurs through muscle bridges, which may be discrete or form an intermingled continuum. These muscle bridges, if disconnected, may dissociate the coronary sinus from the left atrium, in which case the coronary sinus electrograms do not represent left atrial activation, and do not help to understand, or may cause misinterpretation of, the mechanism of supraventricular tachycardia. We report one such case of orthodromic supraventricular tachycardia mediated through the left lateral accessory pathway in which the coronary sinus got dissociated from the left atrium during radiofrequency ablation.