Successful Ablation of Refractory Mitral Annular Atrial Flutter Using Ethanol Infusion in the Vein of Marshall

The vein of Marshall (VOM) is the embryological remnant of the left-sided superior vena cava (SVC). It has been identified as an important trigger for atrial fibrillation (AF)1, in addition to being a conduit for the sympathetic and parasympathetic innervation2,3 of the left atrium, thereby contributing to maintenance of AF.

We discuss a patient with long-standing persistent AF and inducible mitral annular atrial flutter where ethanol infusion within the VOM resulted in successful termination of this refractory flutter.

Case Presentation

A 78-year-old male presented with a history of symptomatic persistent AF for 3 years despite adequate rate control. Over the years, multiple cardioversions were attempted, but each time, he reverted back to AF within a couple of days. AF was accompanied by significant shortness of breath and fatigue. Use of antiarrhythmic drugs was restricted due to a history of liver transplant and drug interactions between the antirejection drugs and antiarrhythmic medications. Therefore, it was decided to attempt catheter ablation for AF.

The patient was in AF on presentation. The procedure was performed under general anesthesia using the Carto mapping system (Biosense Webster, Inc, a Johnson & Johnson company). With pulmonary vein isolation (PVI), AF organized into left-sided flutter with distal to proximal coronary sinus (CS) activation. Based on the electroanatomic map, this was noted to be mitral annular flutter and entrainment from the proximal and distal CS (Figure 1A-B). However, it spontaneously degenerated back into AF, which terminated with posterior wall isolation, and the patient went back into normal sinus rhythm.

The mitral annular atrial flutter was easily inducible with single atrial extrastimuli. A mitral annular line was created connecting the left inferior pulmonary vein to the lateral mitral annulus (Figure 2A). Atrial flutter terminated, with intermittent block across the line based on proximal to distal CS activation with left atrial appendage (LAA) pacing. However, recurrent conduction across the line and incessant mitral annular flutter occurred despite extensive endocardial and epicardial ablation of the CS. It was then decided to perform VOM alcohol ablation.

The CS was cannulated using an ablation catheter (ThermoCool SmartTouch SF, DF curve, Biosense Webster) and a steerable long sheath (Agilis NxT; Abbott). Contrast injection was performed through a Judkins Right (Merit Medical) 3.5 guide sheath to identify the VOM (Figure 3A), which was then cannulated using a Whisper wire. A 2.0 x 6 mm over-the-wire balloon was inserted into the VOM. The vein was occluded with balloon inflation, and a total of 9 cc of alcohol was injected into the VOM (Figure 3B). Atrial flutter terminated during the alcohol injection (Figure 1C). Bidirectional block was confirmed across the lateral mitral annular line with a significant increase in the scar along the mitral annular line region following alcohol ablation (Figure 1D, Figure 3B). The block persisted during the 20-minute waiting period and adenosine administration. The patient remains in normal sinus rhythm at 9-month follow-up based on event monitors, electrocardiogram, and symptom assessment.

Discussion

For over the past 2 decades, PVI has been the cornerstone of ablation therapy for AF.⁴ Unfortunately, in patients with persistent AF, results of PVI alone have been poor. In patients with persistent AF, the VENUS trial5 showed that addition of VOM ethanol infusion to catheter ablation, compared with catheter ablation alone, increased the likelihood of remaining free of AF or atrial tachycardia at 6 and 12 months (49.2% vs 38%; P=.04). In addition, successful perimitral block was achieved in a significantly higher number of patients in the VOM alcohol ablation group (80.6% vs 51.3; P<.001). Kamakura et al⁶ showed that in 713 patients undergoing VOM alcohol ablation, infusion success was achieved in 89% patients, with dissection noted in 10.7%. Successful mitral annular block with first mitral line attempt was seen in 95.8% patients.

With the advent of VOM, we hope to achieve higher success rates with catheter-based ablation for persistent AF. Traditionally, perimitral block could be achieved only in 50%-80% of patients with a lateral mitral annular line, despite CS ablation.^6,7 This has improved significantly with alcohol injection of the VOM by ablating the epicardial connections of the mitral annular flutter circuit. Given the increasingly powerful data for the benefits of maintaining sinus rhythm in patients with heart failure with reduced ejection fraction, new techniques to improve the success rates of ablation in patients with long-standing persistent AF are critical. VOM alcohol injection can be a powerful tool to improve the success rate of both mitral isthmus as well as persistent AF ablation. The specific role of other described techniques for the ablation of persistent AF, such as posterior wall isolation, LAA isolation, and VOM alcohol injection, deserve further studies.

Conclusion

Ethanol injection in the VOM, in addition to endocardial catheter ablation, increases procedural success for perimitral block and maintenance of sinus rhythm in patients with persistent AF. 

Disclosures: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors have no conflicts of interest to report regarding the content herein.

References

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