Mitral isthmus ablation using steerable sheath and high ablation power: a single center experience.
BACKGROUND
Mitral isthmus ablation is challenging. The use of steerable sheath and high ablation power may improve success rate.


METHODS
This single-center, prospective study enrolled 200 patients who underwent ablation for atrial fibrillation (AF), including mitral isthmus ablation. Mitral isthmus ablation was performed using an irrigated ablation catheter via a steerable sheath (endocardium: maximum power: 40/50 W limited to annular end, maximum temperature: 48 °C; coronary sinus [CS]: maximum power: 25/30 W, maximum temperature: 48 °C). Endpoint was bidirectional mitral isthmus block.


RESULTS
Mitral isthmus block was acutely achieved in 182/200 patients (91%). Sixty-nine percent of patients required CS ablation. Mean total ablation time was 13 ± 6 minutes. There was 1 case of acute circumflex artery occlusion. Mean left atrium (LA) diameter was significantly bigger in patients with unsuccessful mitral isthmus ablation (49 ± 4 mm vs. 43 ± 6 mm; P = 0.0007). In redo procedures, the incidence of reconduction at the mitral isthmus, roof and cavotricuspid isthmus was 44%, 37%, and 29%, respectively. Overall incidence of perimitral flutter was 9%. Prior complex fractionated atrial electrogram ablation was a predictor for microreentrant atrial tachycardia (AT) whereas gaps in linear lesions predicted macroreentrant flutters. After a mean follow-up of 20 ± 9 months, 73% of patients remained free from AF or AT.


CONCLUSIONS
We reported on a series of mitral isthmus ablation using steerable sheath and high ablation power (50 W). Larger LA diameter was a predictor of failure to achieve mitral isthmus block. The mitral isthmus had a moderately high incidence of re-conduction but was only associated with a relatively low incidence of perimitral flutter.
Oxford Heart Centre, John Radcliffe Hospital, Oxford, UK.
Kelvin C K
KC
Wong
Norman
N
Qureshi
Michael
M
Jones
Kim
K
Rajappan
Yaver
Y
Bashir
Timothy R
TR
Betts
D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D001282:Atrial Flutter / Q000209:etiology; D062906:Cardiac Catheters; D017115:Catheter Ablation / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D016009:Chi-Square Distribution; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D004739:England; D004867:Equipment Design; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000503:physiopathology / Q000601:surgery*; D015999:Multivariate Analysis; D011446:Prospective Studies; D012008:Recurrence; D012086:Reoperation; D013617:Tachycardia, Supraventricular / Q000209:etiology; D007507:Therapeutic Irrigation / Q000295:instrumentation; D013997:Time Factors; D016896:Treatment Outcome