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.