Abstract 17174: New Criteria for Block Across Anterior Mitral Line That Includes Bachmann’s Bundle in Patients With Scar Perimitral Flutter

Background: The recurrence rate of scar perimitral flutter (SMF) after anterior mitral line (AML) ablation remains high. Epicardial connections from high right atrium (HRA) to high lateral left atrium (HLA) including the Bachmann bundle (BB) plays a significant role in perimitral flutter recurrence. Hypothesis: We hypothesize that block across BB (BBB) during endocardial anterior line ablation reduces recurrence of atrial tachycardia (AT) and SMF. Methods: Patients undergoing left atrial ablation with SMF that were treated with AML were retrospectively enrolled. Pulmonary veins isolation and bidirectional AML block achieved in all patients. Baseline HRA-HLA, final HRA-HLA, and delta HRA-HLA intervals measured. Changes in HLA activation sequence determined. BBB identified when HRA-HLA interval increased with change in HLA activation sequence and confirmed with differential pacing. (Figure 1). The primary endpoint was recurrence of AT/SMF Results: We identified 101 patients, 51% comprised of women, with a mean age of 69. Patients who had AML without evidence of BBB were 48 compared to 53 patients who had AML with evidence of BBB. The mean baseline, final and delta HRA-LAA were 123 ± 42ms, 219 ± 45 ms and 96± 21 ms respectively in patients with BBB. After median follow up of 48 months, AT/SMF recurred in 43 % of patient without BBB vs 15 % in patient with BBB (p<0.008) (Figure 2). In patients with BBB, delta HRA-HLA >107ms discriminated between recurrence and no recurrence (p<0.023ms and 93% negative predictive value) Conclusion: During endocardial AML ablation for SMF, bidirectional block with evidence of BBB is associated with significant reduction in AT/SMF recurrence.