Systematic Evaluation of High-Resolution Activation Mapping to Identify Residual Endocardial and Epicardial Conduction Across the Mitral Isthmus.
OBJECTIVES
This study sought to systematically evaluate the ability of a high-resolution mapping system (Rhythmia, Boston Scientific, Marlborough, Massachusetts) to rapidly and accurately localize residual endocardial and epicardial conduction after mitral isthmus (MI) ablation, facilitating MI block.


BACKGROUND
Achieving conduction block across the mitral isthmus (MI) is challenging.


METHODS
Fifty consecutive patients undergoing MI ablation after pulmonary vein isolation were enrolled. After initial endocardial radiofrequency (RF) ablation across the lateral MI, high-resolution activation mapping of the MI with simultaneous coronary sinus (CS) mapping was performed to verify block or localize residual conduction across the MI during left atrial (LA) appendage and CS pacing. Propagation maps were used to identify residual conduction across the MI as endocardial, via the CS or Marshall tract.


RESULTS
In all 50 patients, after the initial endocardial ablation across the MI, repeat high-resolution mapping of the LA and CS was obtained (median: 3,329 mapped points; 4.0 min of mapping time). The initial endocardial MI ablation resulted in block in 9 of 50 patients (18%). In the remaining 41 patients, the propagation map identified residual conduction in 4 patterns: 1) only endocardial gap in 12 patients (29%); 2) only CS connection in 10 patients (24%); 3) both endocardial and CS connections in 14 patients (34%); and 4) Marshall tract connection in 5 patients (12%). In 8 patients, the propagation map revealed residual conduction, despite differential atrial pacing suggesting bidirectional block. Focal ablation at the identified residual conduction site (median: 0.7 min of RF) resulted in block in 49 of 50 (98%) patients.


CONCLUSIONS
High-resolution propagation maps of the LA/CS rapidly and accurately localize residual endocardial and epicardial conduction across the MI. Focal ablation with short RF time at the identified gap(s) achieved complete block across MI in 98% of cases.
['Sakamoto|Yuichiro|Y|', 'Lockwood|Deborah|D|', 'Yamaguchi|Ryo|R|', 'Yoshimoto|Daisuke|D|', 'Suzuki|Takahiko|T|', 'Ho|Siew Yen|SY|', 'Nakagawa|Hiroshi|H|']
D001281:Atrial Fibrillation D017115:Catheter Ablation D004699:Endocardium D006339:Heart Rate D006801:Humans D011667:Pulmonary Veins
mapping mitral isthmus atrial fibrillation atrial tachycardia catheter ablation