Letter from the Editor

Grilling a Burger in the Winter

Bradley P. Knight, MD, FACC, FHRS, Editor-in-Chief

@DrBradleyKnight

Bradley P. Knight, MD, FACC, FHRS, Editor-in-Chief

@DrBradleyKnight

Atrial-esophageal fistula is a rare but potentially lethal complication associated with left atrial ablation for atrial fibrillation (AF). Many strategies are therefore employed to minimize esophageal injury during AF ablation. These include use of esophageal luminal temperature monitoring, esophageal deviation, esophageal cooling, and limiting the power and duration of energy delivery at left atrial sites when close to the esophagus. One esophageal cooling device that has been evaluated in the EP lab for esophageal protection is the ensoETM device (Attune Medical), which is already commercially available and used in hospitals to induce hypothermia for cerebral protection. The device consists of a dual-lumen tube of silicone through which sterile distilled water is recirculated from the temperature-regulated reservoir of a Blanketrol III (Gentherm Medical) mobile console (the most commonly utilized console for the ensoETM) at a set temperature ranging from 4 to 42°C. 

Most of the published experience of esophageal cooling with the ensoETM device comes from the group at St. George’s Hospital in London. There, Dr. Mark Gallagher and his colleagues have completed enrollment in the IMPACT (Improving Oesophageal Protection During AF Ablation) study, a prospective, double-blind, randomized controlled trial conducted between February 2019 and January 2020. Patients with AF undergoing radiofrequency (RF) ablation under general anesthesia were randomized 1:1 to esophageal cooling with the ensoETM device or to a control group in which a single-sensor temperature probe was placed in the esophagus. Interesting, because intracardiac echocardiography is not routinely used at their institution, the esophageal cooling device was placed by the anesthesiologist after a transesophageal echo (TEE) probe was used to guide the transseptal catheterization portion of the procedure. Placement of the TEE probe did not seem to confound the endoscopy results. Ablation was performed using focal RF with an irrigated, contact force sensing catheter and a three-dimensional mapping system with a power setting of 30-40 Watts guided by standard Ablation Index (AI) settings. Pulmonary vein isolation (PVI) alone was performed in patients with paroxysmal AF, and PVI plus posterior wall isolation (PWI) was performed in most of the patients with persistent AF. In the group with the ensoETM device, the esophagus was cooled to 4°C during left atrial posterior wall ablation. Participants were scheduled to undergo endoscopy seven days after the ablation. Esophageal lesions were graded on a modified Kansas City scoring system. Patients and the endoscopist were blinded to the randomization. Clinical follow-up was at 3 and 6 months, and gastroesophageal reflux and gastroparesis questionnaires were administered.

Enrollment in the IMPACT study took longer than expected because a large number of patients enrolled in the trial apparently did not agree to return one week later for their endoscopy. Therefore, the initial enrollment target was increased from 120 to 188 patients to allow for endoscopic data to be obtained from 60 patients in each group. Preliminary data from this study was presented at the American Heart Association’s (AHA) Scientific Sessions in November 2019 and focused on the endoscopy findings. At the time of the AHA presentation, endoscopy results were available for only 78 patients (40 protected by the ensoETM device, and 38 control patients), and there was already evidence that the device protected against esophageal lesions. Additional data was presented at the AF Symposium in January 2020.

During Heart Rhythm Society 2020 Science, held virtually in May 2020, Dr. Gallagher presented additional data from the IMPACT trial.1 Consistent with earlier reported preliminary data, cooling the esophagus was protective. Any esophageal mucosal injury was seen in 12/20 control patients compared to only 2/20 protected patients, one of which was related to a protocol deviation whereby ablation was performed when cooling was not being delivered. But in this recent presentation, a key unanswered question related to esophageal cooling was also addressed: whether or not cooling the esophagus could interfere with the ability to achieve successful left atrial lesion formation when ablation is performed near the cooling device. Cooling appeared to have no impact on the ability to create RF lesions and to isolate the veins. PVI was achieved in 100% in each group, and first-pass isolation was achieved in 88% in the protected group and 87% in the control group. Posterior wall isolation was equally successful in each group (16/23 in protected group compared to 19/23 in the control group). Procedure, fluoroscopy, and total RF times were the same in each group. Ablation data were the same for each group. There was no difference in force, power, or energy required to isolate PVs. There was no difference in the maximum temperature, baseline impedance, or impedance drop (8-9 ohms). It would have been interesting to see if the baseline temperatures were the same in each group. Complications were rare, and the same in each group. There was no difference in gastroparesis. So far, there is no difference in clinical outcomes, although only 23 of 120 patients have been followed to one year.

It can be more difficult to barbeque a hamburger during the winter unless one has a high-quality grill capable of overcoming the elements. It appears that not only is cooling the esophagus during RF left atrial ablation protective of the esophagus, but it also does not interfere with the ability to ablate the posterior left atrium when using a tool as powerful as irrigated RF energy. 

Disclosure: Dr. Knight reports that he is a consultant, speaker, investigator, and offers fellowship support for Abbott, Baylis Medical, Biosense Webster, Inc., BIOTRONIK, Boston Scientific, Medtronic, and SentreHEART.

References
  1. Late-breaking clinical trials III: all about AFib. Heart Rhythm TV. Published May 8, 2020. Available at https://www.youtube.com/watch?v=23VH2d72NDA. Accessed May 13, 2020. 
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