Fluoroscopic Image LAO 37 degrees projection: The catheters are noted in the HRA, RV, and CS and the ablation catheter in the LA through a transseptal puncture. The ablation catheter is at the ablation site (12 o'clock at the mitral annulus).LAO: left anterior oblique; HRA: high right atrium; RV: right ventricle; CS: coronary sinus; LA: left atrium. His catheter is the ablation catheter.