Adding an ethanol infusion to the vein of Marshall during catheter ablation of persistent atrial fibrillation (AF) increases the chances of maintaining normal rhythm, a new study has shown.

Lead author Miguel Valderrábano, MD, Methodist DeBakey Heart and Vascular Center, Houston, Texas, noted that catheter ablation of persistent AF has suboptimal outcomes, with low single-procedure success and frequent need for repeat procedures.

“The vein of Marshall is an attractive target to improve ablation results, since it contains pro-fibrillatory innervation, AF triggers, and it sits in the mitral isthmus, critical for peri-mitral flutter,” he said. “But all of these mechanisms can be ablated by vein of Marshall ethanol infusion.”

The results were presented March 29 at the “virtual” American College of Cardiology 2020 Scientific Session (ACC.20)/World Congress of Cardiology.

The current study involved 343 patients with symptomatic persistent AF (sustained, lasting more than 7 days) which was refractory to at least one antiarrhythmic drug.

They were randomly assigned to catheter ablation alone (n = 158) or with vein of Marshall ethanal infusion (n = 185). The ethanol infusion was administered in up to four injections of 1 cc from distal vein of Marshall to proximal.

The vein of Marshall group included 15% more patients than the control group in anticipation that some of the procedures would not be possible. Results showed that 30 of the 185 vein of Marshall procedures (16.2%) were indeed unsuccessful.

The primary endpoint of freedom from AF or atrial tachycardia of more than 30 seconds after 3 months with a single procedure and off antiarrhythmic drugs was achieved in 49.2% of the vein of Marshall ethanol infusion group vs 38% of those that did not receive the ethanol infusion (hazard ratio [HR], 0.63, P = .037).

In the per protocol group, the primary endpoint occurred in 51.6% of patients (HR, 0.57, P = .015).

In terms of AF burden, this was zero at 6 and 12-month monitoring in 78.3% of the ethanol infusion group and 67.9% of the control group (P = .011).

The main adverse event in the ethanol infusion group was fluid overload requiring diuretics, which occurred in 14 (7.5%) of 185 patients compared with 2 (1.2%) of 158 patients in the control group. But there were no acute procedural complications directly attributable to the vein of Marshall procedure, Valderrábano reported.  

Discussant for the study at the ACC’s Featured Clinical Research session, Mark Link, MD, UT Southwestern Medical Center, Dallas, Texas, said: “I think this gives us another potential tool for AF.”

“This was a difficult trial to pull off and it looks as though it was pulled off quite well,” he commented. 

“The hypothesis is that the atrial tissue that drains into the vein of Marshall must contain something important for AF, including AF triggers,” Link noted.

He pointed out that greater than 50% of the population had longstanding persistent AF yet 70% of individuals in the whole study had no AF after the 3 months blanking period. “That’s fairly remarkable in my mind for a persistent AF population.”

Link noted that there was a high degree of extra ablation, “so this was an extensive ablation procedure.” 

“What’s coming along is that for persistent AF you need to ablate a lot, and I think this trial shows us that,” he added.

Link asked whether cannulating the vein of Marshall was a difficult procedure to learn.

“We did the first human procedure in 2008 and in our first series our success rate was about 81%, but then we got much better,” Valderrábano replied. “We are now at 89% at our institution. Sometimes you find a vein and it may not be the vein of Marshall, but we are getting better at identifying atrial veins. However, there is no doubt that it takes commitment from the operator to learn it. We’ve had a few people come and visit and it can be learned and reproduced.”

“In this trial we had specific operator training before they could enroll,” Valderrábano added. “You have to put in some effort but it is definitely something that is doable.”

The current study was funded by the National Institutes of Health/National Heart, Lung and Blood Institute. Valderrábano and Link have disclosed no relevant financial relationships.

American College of Cardiology 2020 Scientific Session (ACC.20)/World Congress of Cardiology: Abstract 20-LB-20518-ACC. Presented March 29, 2020.

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