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Figure 2 Patient #6. 12-lead surface electrocardiogram: (A) after atrioventricular node radiofrequency ablation: chronic atrial fibrillation with nodal escape rhythm (QRS 100 ms); (B) during direct His-bundle pacing: paced QRS duration 100 ms, with morphology and electric axis equal to the native QRS; (C) during right apical ventricular pacing: paced QRS duration 160 ms, with extreme left-axis deviation and "left bundle branch block" morphology.