Peri-Mitral Atrial Tachycardia Using the Marshall Bundle Epicardial Connections.

Objectives: The aim of this study was to determine whether re-entrant circuits were associated with the ligament of Marshall (LOM).

Background: Peri-mitral atrial tachycardias (PMATs) following pulmonary vein isolation (PVI) or mitral valve surgery are common.

Methods: Six PMATs involving epicardial circuits were identified from 38 patients. Of these, 4 PMATs involved the LOM (PMAT-LOM, mean cycle length 308 ± 53 ms), as confirmed by the insertion of a 2-F electrode in the vein of Marshall (VOM). All patients underwent PVI and mitral isthmus ablation. The PMAT-LOMs were diagnosed based on left atrium (LA) activation maps that covered <90% of tachycardia cycle length (TCL), and a difference between the post-pacing interval and TCL that was: 1) ≤20 ms at the VOM, the ridge between the left pulmonary vein and appendage, the anterior wall of the LA, and along the 6 to 11 o'clock direction of the mitral annulus; and 2) >20 ms at the distal coronary sinus (CS), the posterior wall of the LA, and the mitral isthmus ablation line (or noncapture). Catheter ablation was performed at the ridge for all PMAT-LOMs.

Results: Three tachycardias were successfully terminated at the ridge, which showed continuous fractionated potential lasting >100 ms, confirming the bidirectional block of Marshall bundle (MB)-LA connections. The remaining tachycardia required ablation for the CS-MB connections, confirming bidirectional block of CS-MB connections.

Conclusions: PMAT-LOMs following PVI or valve surgery accounted for up to 11% of PMATs. The bidirectional block of either MB-LA or CS-MB connections is required to eliminate PMAT-LOMs.