Catheter for AF Maps, Ablates, and Sees Inside the Heart

Daniel M. Keller, PhD

March 25, 2019

LISBON — A lot of functionality has been packed into one balloon catheter for treating atrial fibrillation (AF). The multielectrode, radiofrequency (RF) balloon catheter with integrated mapping and pacing capability plus video camera achieved high rates of pulmonary vein (PV) isolation with short ablation times and a low rate of device-related complications, a trial has shown.

The Luminize catheter (Boston Scientific) consists of six forward-facing electrodes and 12 equatorial ablation electrodes around the outside of the head of the catheter.

Integrated mapping and pacing abilities allowed for real-time assessment of PV isolation and phrenic nerve capture. The built-in cameras validated electrode contact through direct visualization and allowed tailoring the radio frequency dosing based on contact to optimize the ablation.

Presenting on behalf of the investigators of the Assessment of Safety and Performance of the Apama RF Balloon Catheter System to Isolate Pulmonary Veins in the Treatment of Paroxysmal Atrial Fibrillation (AF-FICIENT I) trial, Amin Al-Ahmad, MD, Texas Cardiac Arrhythmia, Austin, explained that the catheter can ablate in different ways.

It can ablate either as a unipolar device, meaning using the poles to the different electrode, or as a bipolar device, where current flows between two adjacent poles next to each other, or finally, multipolar, if all poles are selected. Apical and equatorial electrodes can be combined to best fit the anatomy being lesioned.

For the trial, patients received an RF dose of 6 to 10 watts using the catheter, with confirmation of pulmonary vein isolation using a circular mapping catheter or the Luminize balloon electrodes. At the discretion of the operator, esophageal monitoring or deviation and general anesthesia were used.

This prospective, nonrandomized, multicenter pilot study was carried out in two phases (phase 1, n = 18; phase 2, n = 81).

Enrolled patients were 18 to 75 years old (mean in both phases, 58 years; 68% male; left ventricular ejection fraction, 60%), had symptomatic paroxysmal AF (phase 1, 78%; phase 2, 100%), and had not been successfully treated with class I or III antiarrhythmic drugs.

By phase 2, treatment was almost universally effective in terms of veins isolated and patients successfully treated.

Treatment Performance
Isolation Phase 1 Phase 2
Vein (%, n) 88.9 (64/72) 99.4 (322/324)
Patient (%, n) 77.8 (14/18) 97.5 (79/81)
Ablations/patient (mean ± standard deviation [SD]) 12.3 ± 4.0 8.5 ± 3.6
Procedure time (mean ± SD), min 173 ± 51 79 ± 28
Balloon dwell time (mean ± SD), min 102 ± 52 33 ± 20
Fluoroscopy time (mean ± SD), min 43 ± 17 14 ± 7

Between phase 1 and 2, enhancements were made to the catheter that allowed a greater range of flexibility in steering it and the addition of more electrodes to allow sensing of the signal.

"The procedure time dramatically improved after device enhancements were made from an average of 173 minutes to down to an average of 73 minutes," Al-Ahmad said. "This reflects both the device enhancements and experience with the device."

By phase 2 there were fewer ablations per patient and shorter procedure, fluoroscopy, and balloon-dwell time. There were approximately two applications per vein, with six to 10 ablation lesions per patient in phase 2.

There were no device-related serious adverse effects at 30 days and no evidence of PV stenosis in patients for whom cardiac imaging was available (0/32).

Al-Ahmad noted that a limitation of study results is that there are no data on long-term freedom from atrial fibrillation with this device.

Philipp Sommer, MD, Clinic for Electrophysiology, Ruhr University Bochum, Bad Oeynhausen, Germany, presented commentary on the study. He said many new devices are coming to market, and "all these devices have one thing in common": they want to combine the best design features and functions of different current designs.

Whereas single-tip RF catheters are good for high-resolution mapping and ablation anywhere, they are not good at rapid PV isolation or ease of use, he said. And balloons can do rapid vein isolation and are easy to use, but they currently are limited for high-resolution mapping and ablation in any location. Combining the best aspects of today's separate technologies in the Luminize catheter "is something really nice," as the results of this study show, he said.

Sommer pointed out that some of the strengths of the study are the demographics of the cohort and the data on procedure durations and performance in phase 2. Limitations were the nonirrigated nature of the procedure, raising the possibility of silent embolisms. Esophageal temperature monitoring was not mandatory, with the possibility of thermal lesions. There was no voltage mapping to demonstrate what he called the "level of isolation."

He also commented that postprocedural imaging occurred in only 32 of 99 patients, and without it, one would not know if PV stenosis developed. And finally, he said the device could be "cost-intensive" because of the cameras that are part of it.

In response, Al-Ahmad commented to theheart.org | Medscape Cardiology that Sommer "raised a lot of very important and good points," but cost was not one of them. "Believe it or not, cell-phone camera technology has changed the world, and implementing that kind of technology in a catheter is no longer cost-prohibitive," he said. "In fact, I'm told that this catheter can be on par with any other balloon catheter in terms of cost."

He agreed that the other points Sommer raised are valid and will be taken into consideration with the next study, including esophageal monitoring and MRI of the brain. He explained that MRI would be looking for asymptomatic lesions in the brain that have been reported with all catheters across all technologies, "the significance of which is not entirely clear.... [For] any new catheter, the FDA is going to ask for those data."

He predicts that larger studies should begin by the end of this year. The device is in development and is not available for sale or use yet.

Al-Ahmad has a consulting, royalty, ownership, or stockholder relationship with Boston Scientific. Sommer is an advisory board member and has received lecture honoraria and research funding from Abbott.

European Heart Rhythm Association (EHRA) 2019 Congress: Presentation 182. Presented March 17, 2019.

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