Atrial voltage analysis following vein of marshall alcohol infusion predicts mitral line block
Authors: Taddeucci S , Garibaldi S , Nesti M , Mirizzi G , Startari U , Landra F , Panchetti L , Marchese P , Piacenti M , Rossi A 
Published: May 2024

Abstract

Background
The vein of Marshall (VOM) is a promising therapeutic target for the atrial fibrillation (AF) treatment, fitting perfectly with the "Coumel triangle" as it contains triggers of focal activities and stable reentries, autonomic parasympathetic and sympathetic connection and it represents substrate for perimitral flutters. Lateral mitral line (ML) represents a fundamental part of the anatomical ablation setup for the treatment of AF but its bidirectional block is very difficult to achieve by endocardial ablations. Ethanol infusion into the VoM (VOM-EI) has demonstrated high effectiveness in facilitating ML block. Newly-formed bipolar lesion after VOM-EI is considered an index of effectiveness of the alcoholization procedure. Voltage analysis assessment after VOM-EI in predicting ML block is poorly investigated.

Purpose
To compare unipolar and bipolar low-voltage areas (LVAs) along VOM trajectory after VOM-EI, and their role in predicting ML block.

Methods
We enrolled 59 patients undergoing catheter ablation for persistent AF or mitral isthmus dependent atrial flutter. We performed first a high-density voltage map of the left atrium. After VOM-EI, a LA remap was performed. The area width difference was obtained and defined as ∆LVA (see Figure 1). Normal Bipolar voltage cutoffs were 0.50 mV in case of sinus rhythm or 0.29 mV in case of AF. Unipolar cutoffs were respectively 2.7 mV in sinus rhythm and 1.1 mV in AF. The anatomical lesions set, after VOM-EI, included wide antral PVI, linear lesion for dome and ML isthmus following the newly-formed lesion after the VOM-EI. Systematic lines block validation was performed. ML block was defined after coronary sinus electrograms sequence inversion (septal-to-lateral) during left atrial appendage pacing. In case of residual conduction gaps, RF applications into the coronary sinus-great cardiac vein were done to target residual epicardial gaps. Ablation time to obtain ML block (AblTime) was obtained.

Results
In our group, 56/59 patients (94.5%) achieved mitral isthmus block. Bipolar and unipolar low voltage areas after VOM-EI were 9.9 ± 6.9 cm2 and 12.2 ± 5.9 cm2 respectively. Bipolar ∆LVAs were significantly lower compared with unipolar ∆LVA (8.2 ± 6.5 cm2 vs 9.4 ± 6.0 cm2; p= 0.03). A strong linear correlation between AblTime and bipolar ∆LVA (R: 0.76) and a significant correlation between AblTime and unipolar ∆LVA (R: 0.6) were found (Figure 2). Patients that required coronary sinus applications to reach ML block (13/59, 22%), presented lower ∆LVAs at logistic regression both at bipolar (p&lt;0.01) and unipolar (p=0.03) analysis.

Conclusions
Unipolar and bipolar voltage analysis along the mitral isthmus trajectory predicts ML block achievement, with VOM-EI inducing wider unipolar LVAs than bipolar LVAs. Furthermore, wider unipolar and bipolar LVAs post VOM-EI are linked to a shorter AblTime and an increased probability of avoiding the need to target epicardial gaps via the CS musculature.LVA along VOM territory after VOM EI∆LVAs linear correlation with AblTime