Vein of Marshall Alcohol Ablation: Workflow and Feasibility of Establishing a Program

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EP LAB DIGEST. 2024;24(5):1,26-30.

Pulmonary vein isolation (PVI) remains the cornerstone of rhythm control in AF ablation strategies.¹ Mitral annular flutter following scar modification, prior surgical interventions, and PVI is not uncommon. The vein of Marshall (VOM) and ligament of Marshall play a significant role in the initiation and maintenance of atrial fibrillation (AF) and participating in mitral re-entry.² In complex AF ablation requiring left atrial (LA) scar modification or mitral annular flutter cases, achieving complete mitral isthmus conduction block is warranted. This can be challenging due to the presence of epicardial fibers, the risk of left circumflex artery injury, and the heat sink effect.³ 

Alcohol ablation of the VOM has shown high efficacy in managing both AF and atypical left-sided atrial flutters (AFLs).^4,5 At Houston Methodist Hospital, Dr Valderrabano has been a pioneer in alcohol VOM ablation. Under his guidance, the VOM ablation program was initiated in 2020 at Houston Methodist Willowbrook and Houston Methodist The Woodlands Hospitals. This technique has mainly been pursued in patients with long-standing persistent, recurrent AF patients undergoing redo AF ablations, and those with atypical mitral annular flutters. In this article, we discuss our approach to VOM alcohol ablation, workflow and feasibility of establishing a program, and share 2 brief case studies.

Approach to VOM Alcohol Ablation

Preprocedural Planning
Standard preprocedural planning for AF ablation is employed. The absence of left atrial appendage (LAA) thrombus is ensured using transesophageal echocardiography, computed tomography (CT) angiography of the LA, or intracardiac echocardiography during the procedure. For redo ablations, a CT angiogram of the LA is obtained to evaluate the LA and PV anatomy.

All procedures are performed under general anesthesia, with low-dose paralytics used to allow for low tidal volume ventilation during the procedure.

Access
In addition to the standard femoral venous access for AF ablation, right internal jugular (IJ) vein access is obtained using a micropuncture needle under ultrasound guidance. A 9 French (F) vascular introducer is then placed in the right IJ.

VOM Engagement
A straight left ventricular CPS sheath (Abbott) is advanced into the right atrium over a Wholey wire. The coronary sinus (CS) is engaged using an AL-2 catheter, and the CPS sheath is advanced into the main body of the CS. A left internal mammary artery (LIMA) guide catheter is subsequently advanced into the CS through the CPS sheath. A contrast injection is performed to identify the presence and location of the VOM. It has been reported that the VOM is absent in 20% of patients.⁵

Identification of VOM
The VOM is best identified in the right anterior oblique (RAO) caudal projection. Its ostium tends to be proximal to the Vieussens valve and usually oriented towards the LAA. A mapping or ablation catheter placed in the LAA helps confirm the location and identification of the VOM.
Though alcohol ablation of the VOM via a right femoral venous approach using an Agilis sheath is also feasible, we primarily prefer the IJ approach.

Figure 1 demonstrates the LA venous anatomy, including typical orientation of VOM.⁶

Alcohol Ablation of VOM
Once the VOM is identified, a coronary 0.14” wire is advanced into the VOM. An over-the-wire balloon is inflated to occlude the VOM, followed by the injection of 10 cc of alcohol. It is crucial to slowly administer alcohol (approximately 3 cc over 1 minute) to avoid extravasation proximally. A small contrast injection may be performed prior to alcohol injection to confirm balloon occlusion of the VOM.

Mitral Conduction Block
Alcohol ablation of the VOM alone typically does not achieve complete mitral isthmus block. Endocardial ablation spanning the posterior LA from the left inferior pulmonary vein (LIPV) to the mitral valve is also necessary. If complete mitral isthmus block is not achieved, additional ablation may be required in the CS near the ostium of the VOM.

Postprocedural Planning
The 9F venous sheath is removed, employing manual pressure or a figure-of-8 suture for hemostasis after ablation completion and reversal of anticoagulation with protamine. A standard post-AF ablation protocol is followed. Colchicine may be used for pericarditis.

Case #1
A 64-year-old male with a history of prior AF ablation including PVI and LA substrate modification presented with recurrent persistent atypical AFL. LA activation mapping revealed a mitral annular flutter. 

Video 1 showcases a counterclockwise mitral AFL with the propagation map demonstrating an endocardial block and evidence of slow epicardial conduction. Initial endocardial mitral ablation resulted in no change in the mitral flutter cycle length.

Following the initial approach of endocardial mitral ablation, alcohol VOM ablation was then performed (Figure 2). Remarkably, AFL terminated during the first injection of alcohol, indicating the effectiveness of the procedure in real time (Figure 3). A total of 10 cc of alcohol was injected into the VOM. Subsequently, a mitral isthmus conduction time of 151 msec was achieved, suggesting complete block.

Case #2
A 57-year-old male patient with prior history of AF ablation 6 years ago presented with symptomatic recurrent atypical AFL with rapid ventricular response, recurrent after cardioversion. The patient was intolerant to medical therapy and opted for a repeat ablation procedure. 

Initial LA and right atrial maps demonstrated isolated PVs and block along the cavotricuspid isthmus. During transseptal puncture, the patient had induction of AF. Atypical flutter could not be induced during the case, and therefore, it was decided to proceed with posterior wall isolation and mitral isthmus ablation.

After confirming isolation of all 4 PVs and posterior wall isolation with linear ablation along the LA roof and floor, endocardial linear ablation from the LIPV to the mitral valve was performed. Figure 4a demonstrates persistence of conduction along the mitral valve isthmus.

Alcohol VOM ablation was then performed. Video 2 demonstrates the VOM during contrast injection through the LIMA guide catheter. After occluding the VOM with a 2.0 x 6 balloon, 10 cc of 99% alcohol was injected.

Figure 4 demonstrates changes in CS activation while pacing from the LAA, after alcohol injection.

Mitral isthmus block was then confirmed with both pacing and voltage mapping. Figures 5A and 5B demonstrate pre- and post-ablation maps.

Discussion
The termination of AFL during VOM alcohol ablation in case 1 and change in CS activation in case 2 highlight the critical role the VOM plays in the maintenance of atrial arrhythmias, particularly in cases refractory to standard ablation techniques. Both cases underscore the potential of VOM alcohol ablation as a complementary strategy in achieving rhythm control in patients with complex AF histories, including those with previous ablations who have failed to maintain sinus rhythm.

The ability to reliably achieve durable mitral isthmus block with VOM alcohol is a tremendous advancement in the management of complex atrial arrhythmia ablation management. 

Since incorporating VOM alcohol ablation as part of our AF program, more than 100 cases of VOM alcohol ablation have been performed at Methodist Willowbrook and Houston Methodist The Woodlands Hospitals. While patient outcomes have improved, we have not noticed significant changes in EP laboratory efficiency by incorporating this additional technique. It has added only an additional 20 minutes to the standard AF ablation procedure time. Potential complications of alcohol VOM ablation include inadvertent internal jugular arterial puncture and neck hematoma, pericardial effusion, CS dissection, and higher risk of pericarditis post ablation. We have not experienced any major complications or mortality associated with VOM alcohol ablation.

Our experience demonstrates the procedural feasibility and clinical efficacy of integrating VOM alcohol ablation into the AF management repertoire of community hospitals, expanding the array of therapeutic options available in these settings.

Conclusion
Establishing a VOM alcohol ablation program provides a valuable addition to the armamentarium against AF and its associated arrhythmias. The workflow and feasibility of integrating this advanced ablation technique highlight its potential in enhancing rhythm control outcomes in a broader patient population. Further studies and longitudinal data are necessary to fully understand the long-term benefits and risks associated with this procedure. However, early results are promising and pave the way for more widespread adoption of this technique.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest and report no conflicts of interest regarding the content herein. Dr Koranne reports a consultant agreement with Abbott, and support for attending meetings and/or travel from Abbott and Boston Scientific. Dr Valderrabano reports consulting fees for Abbott, Biosense Webster, CathVision, CIRCA Scientific, Johnson & Johnson Medical Device Business Services, and Volta Medical, and payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing, or educational events for the Heart Rhythm Society.