Most Patients Free of AF 1 Year After Visually-Guided RF Ablation

Daniel M. Keller, PhD

July 29, 2020

One-year results with a radiofrequency balloon catheter to isolate pulmonary veins (PV) when treating paroxysmal atrial fibrillation (AF) show that 84% of patients remained free of AF and nearly as many were free of AF, atrial flutter, or atrial tachycardia.

The Luminize (Boston Scientific) balloon catheter consists of 12 equatorial electrodes around its head that can be customized to deliver variable power plus a camera for visual guidance of pulmonary vein anatomy. The catheter's mapping and pacing functions allow real-time assessment of PV isolation and phrenic nerve capture.

The new data from the AF-FICIENT I trial were presented at the virtual European Heart Rhythm Association (EHRA) Congress 2020. Initial results were presented at EHRA 2019.

The first phase of the trial tested the original design of the device in 18 patients and the second phase involved 81 patients using an enhanced catheter design for increased sheath steerability and activated pacing and sensing electrodes. Ablation was multipolar with a power of 6 to 10 watts, and PV isolation was confirmed with a circular mapping catheter or the balloon's electrodes.

"One important qualitative observation over the course of the trial was that the separate circular mapping catheter really was not required, as the many electrodes on the RF balloon were quite sufficient," noted Vivek Reddy, MD, Icahn School of Medicine at Mount Sinai in New York City.

The 99 patients, ages 18 to 75 years, had symptomatic paroxysmal AF unresponsive to class I or III antiarrhythmic drugs and were followed after ablation at intervals up to 12 months. Early end points looked at the rate of successful PV isolation and major adverse events. The 12-month assessment focused on freedom from AF, atrial flutter, or atrial tachycardia (AF/AFl/AT), and serious adverse events.

Patient characteristics were similar in phases 1 and 2 of the study: paroxysmal AF 78% vs 100%, respectively; mean age 58 years; 68% male; left ventricular ejection fraction 60%; and left atrium size 36 vs 40 mm, respectively. About one-third received general anesthesia and the rest received conscious sedation. Coronary artery disease was more prevalent in phase 1 (28% vs 5%), as was chronic obstructive pulmonary disease (11% vs 3%).

At 12-month follow-up, recurrence-free rates were very similar, whether looking only at patients in phase 2 or when combining all phase 1 and 2 patients. For phase 2 patients only, 85.9% were free of AF (95% CI, 76.1% - 92.0%) and 78.1% were free of AF/AFl/AT (95% CI, 67.2% - 85.8%).

Experience and Device Improvements

As operators gained experience and with improvements in the catheter, mean procedure times decreased between phase 1 and 2 (157 vs 71 min), as did left atrium dwell times (92 vs 29 min) and fluoroscopy times (43 vs 13 min), and there were fewer RF applications in phase 2.

By phase 2, treatment with the investigational device was almost universally effective in terms of veins isolated and patients with complete PV isolation. For phases 1 and 2 combined, 97.5% of PV's were isolated (99.4% in phase 2) and 93.9% of patients had complete isolations (97.5% in phase 2).

No device-related serious adverse events occurred 30 days or 12 months after the procedure, including stroke, atrioesophageal fistula, phrenic nerve injury, or PV stenosis.

The study was limited by relatively few participating centers and operators. Additional studies are investigating safety regarding esophageal lesions, asymptomatic cerebral lesions using MRI, and PV anatomy using cardiac CT and MRI. "Importantly, we did not have any data on lesion durability, and future remapping studies are required," Reddy said.

Commenting on the study to theheart.org | Medscape Cardiology, Afzal Sohaib, MBBS, PhD, from St. Bart's Hospital, London, called the Luminize catheter "quite an impressive piece of kit because it actually lets you directly look inside the left atrium with a camera so you can actually see the veins."

Although he said the outcomes are consistent with results using currently available technologies, "it's not a randomized controlled trial. It's a single-arm study. It doesn't allow us to compare it head to head with existing technologies."

"The next step really for this technology is to show that it adds value to what the existing technologies offer, either through efficacy, or through safety, or procedure times," since "3-D electro-anatomical mapping technologies in existence do allow you to construct a pretty good geometry of the left atrium," Sohaib said.

Reddy is a consultant for Boston Scientific and for Apama Medical, in which he holds an equity interest. 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. March 29-31, 2020.

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