Simplified stepwise anatomical ablation strategy for mitral isthmus: efficacy, efficiency, safety, and outcome

Figure 1. Overview of the stepwise strategy for MI ablation from Step 1 to Step 5. Endocardial MI and anterior antrum of LPV ablation in Step 1; posterolateral LA ablation in Step 2; epicardial ablation within CS/VOM in Step 3; CS/VOM isolation in Step 4; breakthrough site ablation in Step 5. CS, coronary sinus; LA, left atrium; LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LPV, left pulmonary vein; LSPV, left superior pulmonary vein; MI, mitral isthmus; VOM, vein of Marshall.

Figure 2. Definition of MI block (bidirectional block on both endocardial and epicardial surface). Pacing comes from the lateral side of the MI line by the multipolar electrode catheter in CS, while recording is done by the ablation catheter on the other site of the MI line in both the endocardium and epicardium. Then, pacing is done by the ablation catheter, and the recording is in the multipolar electrode catheter. Pacing from one side of the MI line. Activation was terminated at the MI line on the opposite site in both the endocardium and epicardium. CS, coronary sinus; LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; MI, mitral isthmus.

Figure 3. Position of the ablation catheter from the ostium to distal-end of the VOM in Step 3. (A) Fluoroscopy and the 3D electroanatomical system showing an ablation catheter in the ostium of the VOM, and a multipolar electrode catheter in the CS/GCV. (B) Fluoroscopy and the 3D electroanatomical system showing an ablation catheter in the VOM crossed the MI line and located at the epicardial surface of the ridge between LAA and left pulmonary vein, and a multipolar electrode catheter in the CS/GCV. CS, coronary sinus; GCV, great cardiac vein; LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; MI, mitral isthmus; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein; VOM, vein of Marshall.

Figure 4. Position and direction of the ablation catheter for CS isolation in Step 4. The ablation catheter was rotated in the CS to locate and ablate the residual musculature lateral to the MI line in order to isolate the CS. The presentation of different vector directions with near-field potential during catheter rotation was signed as the ablation target in Step 4. CS, coronary sinus; LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; MI, mitral isthmus.

Figure 5. Potentials of the ablation target in Step 5. In comparison with MAP 3–4, MAP 1–2 was located nearer the MI line. During the distal CS pacing, the earlier activation site with complex component potential in MAP 1–2 indicated that MAP 1–2 was on the conduction breakthrough site. MAP, mapping; CS, coronary sinus; LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; MI, mitral isthmus.