A case of paroxysmal rate dependent intra-His bundle block

We present a symptomatic bradycardia-dependent paroxysmal atrio-ventricular (A-V) block occurred within the bundle of His. Paroxysmal A-V block was caused by atrial or ventricular premature beats and also by sinus slowing. This case also showed tachycardia-dependent A-V block within the bundle of His. We also discussed the controversial mechanisms of paroxysmal A-V block.