"Three-level shock" in ablation-refractory paroxysmal atrial fibrillation.

His-bundle ablation is a very effective method to control drug-refractory supraventricular arrhythmias. We present a 69-year-old woman with paroxysmal atrial fibrillation, in whom several attempts of unipolar and bipolar His-bundle ablation were ineffective. Ultimately a stable 2/1 atrioventricular block was induced when three successive shocks of 400 W were applied. The first shock was given in that position with the largest His-potential deflection. The other two shocks were applied at catheter positions more distal and more proximal from the first one, respectively. We suppose that the initial lack of success was due to an atypical atrioventricular junction anatomy.