Ridge-related reentry despite apparent bidirectional mitral isthmus block.
Verification of bidirectional block is important for mitral isthmus (MI) ablation. However, recurrent perimitral reentry exists despite apparently MI block.



The purpose of this study was to identify and investigate the characteristics of the ridge breakthrough despite apparent bidirectional MI block and related reentry.



In 60 patients undergoing MI ablation and achieving the criteria of bidirectional block when assessed on the line, the pattern under differential pacing was reassessed at the ridge away from the line to check whether a breakthrough existed. Also, activation and entrainment mapping was performed in 7 patients with ridge-related reentry (RRR) to investigate its possible mechanism.



A ridge breakthrough was found in 7 of 60 patients (11.7%) apparently fulfilling the criteria of bidirectional block. The delay from pacing artifact during distal coronary sinus pacing was shorter at the ridge than on the line (95.6 ± 11.7 ms vs 130.9 ± 15.3 ms; P < .001). In 7 patients with RRR, the left atrial endocardial activation time accounted for 58.5% ± 3.2% of the tachycardia cycle length (TCL) and wide double potential could be recorded on the line. The post-pacing interval (PPI) - TCL after entrainment at the ridge was shorter than that on the line (11.4 ± 3.9 ms vs 34.3 ± 6.6 ms; P < .001), and in 2 patients in whom entrainment from the coronary sinus was possible, the PPI - TCL was 15 and 18 ms, respectively.



Apparent bidirectional MI block despite a ridge breakthrough is not uncommon and may lead to RRR, while the line is not part of the reentry.
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Chen-Xi
CX
Jiang
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Jian-Zeng
JZ
Dong
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
De-Yong
DY
Long
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Rong-Hui
RH
Yu
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Ri-Bo
RB
Tang
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Cai-Hua
CH
Sang
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Man
M
Ning
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Song-Nan
SN
Li
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Xue-Yuan
XY
Guo
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Xin
X
Du
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Rong
R
Bai
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Nian
N
Liu
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Jia-Hui
JH
Wu
Department of Cardiology/Atrial Fibrillation Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China. Electronic address: chshma@vip.sina.com.
Chang-Sheng
CS
Ma
D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000000981:diagnostic imaging; D001281:Atrial Fibrillation / Q000503:physiopathology / Q000601:surgery*; D018780:Body Surface Potential Mapping; D017115:Catheter Ablation / Q000009:adverse effects / Q000379:methods*; D004699:Endocardium / Q000601:surgery; D005260:Female; D006325:Heart Atria / Q000503:physiopathology / Q000601:surgery*; D006329:Heart Conduction System / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000601:surgery; D011667:Pulmonary Veins / Q000601:surgery*; D012086:Reoperation; D017211:Treatment Failure
Ablation; Atrial fibrillation; Atrial tachycardia; Lateral ridge; Mitral isthmus