Cooling Device Limits Esophageal Lesions From AF Ablations

Daniel M. Keller, PhD

July 29, 2020

Repurposing a device meant to cool patients after surviving a cardiac arrest allows cardiologists to minimize esophageal injury during radio frequency ablation for atrial fibrillation (AF), new research suggests.

The device (ensoETM, Attune Medical) is a single-use silicon tube inserted into the esophagus, similar to a standard gastric tube but with a closed-loop system into and out of which water circulates from a console.

Previous strategies to protect the esophagus have been inadequate — from proton pump inhibitors, to esophageal deflection, to infusing small amounts of cold water at a time into the esophagus, the researchers note. And esophageal temperature-monitoring probes could increase thermal injury and slow the procedure.

Esophageal injury is an "enormous problem" during AF ablation, accounting for "about half of the mortality occurring during the procedure, by far the largest cause of death," according to Mark Gallagher, MD, consultant cardiologist at St. George's University Hospitals NHS Foundation Trust, University of London.

Looking for a better alternative to current esophageal protection approaches, "we found it in our own intensive care unit," he said during the virtual European Heart Rhythm Association Congress 2020.

The ensoETM is approved in the United States and Europe for body-temperature control, either warming in the intensive care unit after surgery or for burn victims, or for cooling after head trauma, cerebral hypoxia, or in cases of high fever.

For the Improving Esophageal Protection During AF Ablation (IMPACT) study, 188 patients were randomly assigned to esophageal placement of the cooling device (protected group) or an esophageal temperature probe (control group) prior to AF ablation. Both patients and endoscopy adjudicators were blinded to treatment.

About 30% in each group dropped out after refusing later endoscopies to assess esophageal injury, leaving 60 patients for analysis in each group, which met the calculated number for sufficient power of the study.

To classify esophageal injury, two St. George's Hospital gastroenterologists designed a nine-step grading scale, ranging from 0 (normal) to 6 (perforation/fistula), with 4a/b denoting a superficial ulcer clean or with clot and 5a/b denoting a deep ulcer clean or with clot. These same gastroenterologists did the endoscopies.

"The device protected the esophagus significantly from mucosal injuries, so burns to the esophagus [were] significantly more common in the unprotected group," Gallagher said. At 7 days, 93% of the protected group had no significant esophageal abnormality, compared with 70% of the control group (< .001).

Any degree of mucosal injury occurred in 3.3% of protected patients and in 20.0% of control patients (P =.008). There was a trend toward a lower incidence of gastroparesis among the protected group (2/60 vs 6/60, respectively; = .27). The only other significant difference in mucosal injury was 0 vs 4 grade 1 (erythematous) lesions, respectively (=.04).

One grade 4a lesion occurred in the protected group because of a protocol violation, in which the operator went back at the end of the procedure to ablate a reconnection, not realizing that the device had already been switched off, Gallagher said.

Procedure duration averaged 186 minutes and varied between groups by less than 1 minute. The difference in fluoroscopy time was less than 15 seconds during a mean of 11 minutes. One patient in each group had a hospital stay of more than 1 night.

At 3 months, there were no significant differences in gastroparesis symptoms index or in gastroesophageal reflux disease scores on the Gastroesophageal Reflux Disease Questionnaire.

Of 27 control patients followed up at 4 months, four had a recurrence of atrial tachycardia or fibrillation, compared with three recurrences among 17 protected patients. Success rates, meaning freedom from AT/AF, for the groups were similar at 6 months.

Which patients would develop lesions was largely unpredictable, but there was a trend toward more lesions in patients who had a posterior wall line. "Performance about that line did increase the risk of plexus injury and of mucosal injury, not surprisingly," Gallagher said. "Other than that, we were not good at predicting who's going to get a lesion." Although the literature suggests patients with a body mass index greater than 26 kg/m2 would be most at risk, "that's not our experience."

Gallagher and colleagues found no downsides to using the esophagus-protection device. "It does not prevent us from constructing effective lesions, does not prevent us from isolating the pulmonary veins. It does not prevent us from isolating the posterior wall. It does not require us to do more burning or do a longer procedure or deliver more fluoroscopy," he said.

Commenting to theheart.org | Medscape Cardiology, consultant electrophysiologist Afzal Sohaib, MBBS, PhD, St. Bart's Hospital, London, called the study "impressive" with "some interesting results" using a common ICU technology to reduce the risk for AF ablation-related esophageal fistula, "which is often a life-threatening complication when it happens, but thankfully, it's a very rare complication."

The problem with having such a rare complication is it is difficult to get sufficient numbers to show that an intervention to reduce the complication is effective. "What Dr Gallagher and the team at St. George's have done is they've used a surrogate marker, which is looking at the endoscopic appearance of the esophagus. So when you do an endoscopy, you can see alteration of the esophagus after an AF ablation. And the thoughts go that those are the precursor lesions, which in some patients may progress to a full-on fistula and all the ramifications associated with that," he explained.

So although the cooling intervention "was actually incredibly effective at reducing the incidence" of esophageal lesions...it'll be very difficult to demonstrate whether reducing the incidence of all of this translates into reduced atrioesophageal fistula down the line," Sohaib said. "But saying that, I think it's pretty compelling data to suggest that it may well do that."

In reply, Gallagher told theheart.org | Medscape Cardiology by email, "We know that a minority of mucosal lesions progress to fistula. There is a reasonable body of evidence to suggest that the incidence of these lesions is a useful surrogate for risk of fistula."

Because the ensoETM device cools from the luminal side of the esophagus but the heat is coming from the outside, where endoscopy would not detect lesions, one may wonder if the device is protecting the entire wall thickness.

"We do expect that protection is better on the layers closest to the lumen. We have seen a trend toward reduced gastroparesis in the protected patients, suggesting that protection extends quite deeply," he said. "Injury to the esophageal muscular layer is being assessed by MRI in other centers."

Caveats to the study and the technique Sohaib cited are the need for general anesthesia, the relatively small number of subjects, and whether the data will translate into actual important clinical outcomes. "But from what they've presented, it seems to be a relatively straightforward device to use in this setting," he said.

Asked whether he would consider using the cooling device in practice himself, Sohaib said, "Potentially…. This is probably better than a lot of other data I've seen in this area." But he would want to see all the data in a published paper first.

The study was supported principally by the charity, Cardiac Risk in the Young, which paid the salary of the study coordinator. Attune Medical provided the ensoETM device free of charge and covered the cost of the endoscopy and incidental expenses. Within the past 10 years, Gallagher has acted as a paid speaker or consultant for Biosense Webster, Medtronic, and Cook Medical, and has received research support from Medtronic, Boston Scientific, Biotronik, and Attune Medical. Sohaib has received speaker fees from Daiichi Sankyo and Bayer, and previously served on an expert panel for Abbott Medical.

European Heart Rhythm Association (EHRA) Congress 2020: Presented online March 29-31, 2020.

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