Abstract 3369: Association Between Bi-directional Mitral Isthmus Block and Atypical Flutter Following Left Atrial Linear Ablation in Patients with Symptomatic Atrial Fibrillation

Background: Incomplete or unidirectional mitral isthmus block (MIB) during left atrial linear ablation (LALA) for atrial fibrillation (AF) may be proarrhythmic, and is the most common target for repeat ablation in patients with atypical atrial flutter (AAFL) after LALA. Objective: To determine if achieving bidirectional MIB during LALA will reduce occurrence post-ablation AAFL and/or recurrence of AF. Methods and Results: Fifty-six consecutive patients (pts), 49 males and 7 females, mean age 59±8 years, who underwent LALA for symptomatic, persistent (61%) or paroxysmal (39%) AF were evaluated. Thirty-four pts had been previously ablated, none had MIB from the first ablation. All pts underwent LALA including two encircling lesions around the right and left pulmonary veins, a line at the roof of the left atrium between the two circles, and a line from the lateral mitral valve annulus (MVA) to the left circle with adjunctive coronary sinus ablation as needed to achieve MIB. Thirty pts had an additional line from the septal MVA to the right circle. Bi-directional MIB was documented by pacing from the left atrial appendage and proximal coronary sinus. Bi-directional MIB was achieved in 38 pts (68%), with ablation in the coronary sinus required in 87.5% of pts. Thirty-seven pts underwent LALA with a standard 8 mm tip (Blazer™ or Navistar™) catheter and 19 pts with saline-irrigated catheters (ThermoCool™, Chili™). Patients were followed for 6±2 months. AAFL occurred in 15 pts (27%), and 17 pts (30%) had recurrence of AF. In pts with AAFL, 8 had documented bi-directional MIB during ablation and 7 did not. The odds of AAFL was 7.6 times higher in pts without MIB compared those with MIB (p=0.02); adjusting for age, gender, diagnosis, type of catheter, coronary sinus ablation and history of previous ablation. This study did not show similar association between recurrence of AF and MIB (p=0.5). Conclusions: Achieving bi-directional MIB will reduce incidence of post-ablation AAFL significantly. Recurrence of AF is not reduced by achieving bi-directional MIB.