Alternative strategies to improve success rate of mitral isthmus block

Figure 1. Variable ablation lesion sets for MI block; A: Simple endocardial MI ablation (yellow arrow), B: additional ablation (purple dots) within distal CS (white arrow), C: new separate endocardial MI ablations (blue arrow), Yellow balls indicate ablation points inside the CS, D: anterior line (green arrow) connecting from the roof line to the mitral annulus. Yellow balls indicate ablation points inside the CS. CS = coronary sinus, MI = mitral isthmus.

Figure 2. Left panel (A): Modified technique of vein of Marshall (VOM, arrows) venography using an irrigated catheter (left anterior oblique 40° view). Contrast dye was injected through the irrigated-tip ablation catheter. a: a 7-Fr CoolFlex (M curve) 4-mm-tip irrigation catheter was engaged in the ostium of the VOM. b: a 7-Fr Duo-decapolar deflectable catheter was placed in the right atrium and coronary sinus. c: a 7-Fr circular duo-decapolar mapping catheter (Lasso) in the left superior pulmonary vein. d: a 5-Fr reference catheter in the right coronary cusp. Right panel (B): The endocardial ablation points (white dots) are shown on a shell of the left atrium, CS, and stump of the VOM (yellow arrow), which were constructed using a 3-dimensional electroanatomical mapping system (EnSite, NavX). Blue balls at the VOM stump (yellow arrow) indicate the final radiofrequency application site (within CS). The red arrow indicates the ablation site where the mitral isthmus block was achieved. CS = coronary sinus, VOM = vein of Marshall.

Figure 3. Flow chart of the study population selection process. AF = atrial fibrillation, RFCA = radiofrequency catheter ablation.

Figure 4. Flow chart of the ablation process for achieving perimitral block in the study population. CS = coronary sinus, MI = mitral isthmus, VOM = vein of Marshall.

Figure 5. Kaplan–Meier curves for recurrence of atrial tachyarrhythmia according to the results of PMB. The term PMB indicates block either in the mitral isthmus or in the anterior line. PMB = perimitral block.

Figure 6. Anterior line ablation after failure of the MI ablation caused significant conduction delay of the LAA. The anterior ablation was performed during high right atrial pacing (HRA 9,10). The lasso catheter was placed in the LAA. At baseline, the stimulus to the earliest LAA potentials was 112 ms (A). However, the interval increased to 157 ms during the anterior ablation (B) and finally increased to 201 ms at the end of ablation (C). LAA activation occurred after onset of the QRS complex after achievement of anterior line block. The follow-up echocardiography did not demonstrate the late diastolic or mitral A wave during sinus rhythm, which suggested a significant intra-atrial conduction delay with ineffective left atrial emptying (D). LAA = left atrial appendage, MI = mitral isthmus.