Contrast injection of the left (A) and right (B) coronary arteries shows course of epicardial coronary arteries prior to injection, to ensure adequate distance from ablation sites. RA=right atrial catheter, His=His bundle catheter, RV=right ventricular catheter, CS=coronary sinus catheter, JL4=Judkins left coronary catheter, JR4=Judkins right coronary catheter