Ablating the ventricular insertion of atrio-fascicular Mahaim fiber: what selection criteria should we use?

We reported a patient who underwent RF ablation of the distal insertion of an atrio-fascicular accessory pathway with decremental properties because of inability to map a suitable potential alongside the tricuspid annulus. Small, discrete potentials resembling those of purkinje fiber were found at right ventricular apex, all these potentials showed early activation during tachycardia preceding the QRS onset of various degrees. Pace mapping helped to localize the presumed main distal insertion of the atrio-fascicular AP in a region where a damage of the His-purkinje system may ensue. This case report describes catheter ablation of an atriofascicular accessory pathway by targeting its distal (ventricular) insertion site.