Conformable, ‘single-shot’ pulsed field ablation catheter scores high for pulmonary vein isolation

A novel “single-shot,” large-lattice pulsed field ablation (PFA) catheter that conforms to diverse left atrial and pulmonary vein anatomies is safe and efficacious for isolating pulmonary veins in patients with paroxysmal atrial fibrillation (AF), as shown in a first-in-human trial.

Called Sphere-360, the device is an 8-Fr sheathed, over-the-wire, conformable-tip lattice catheter. It has electromagnetic sensors linked to a mapping system that allows tracking, shape visualization, catheter orientation, tagging, as well as the creation of anatomical/activation/voltage maps, reported first study author Dr Vivek Reddy of the Icahn School of Medicine at Mount Sinai in New York, New York, US, at EHRA 2024.

The catheter expands in three shapes, up to 34 mm in diameter, with an actuator that is located on the handle. Six independently and sequentially energized sections deliver pulsed-field energy—monopolar, biphasic waveforms that last about 5 seconds for each application, Reddy explained.

Sphere-360 was designed to avoid serial repositioning and rotation, provide all-in-one mapping and ablation via a single transeptal access, and be linked to a dedicated electroanatomical mapping and magnetic navigational system to support a minimized fluoroscopy approach to pulmonary vein isolation, he added.

First-in-human trial

A total of 85 patients (mean age 58.3 years, 56 percent male) with paroxysmal AF participated in the trial. These participants had at least two ECG-documented AF episodes within 12 months of enrolment and had inadequate response of intolerance to at least one class I-IV antiarrhythmic drugs. None of them had continuous AF lasting more than 7 days, body mass index of 40 kg/m² or greater, left atrial diameter of >50 mm, or reduced ejection fraction.

Pulmonary vein isolation was performed using Sphere-360 by a total of six operators at three sites, with a target of four applications per pulmonary vein. Reddy noted that the pulse waveform and the system were optimized throughout the trial to achieve the best possible lesion durability. As a result, the waveform evolved from PULSE1 (n=30) to PULSE2 (n=20) and, finally, to PULSE3 (n=35).

All patients were followed-up for 1 year, with an optional invasive remapping conducted around 75 days postablation. Following the 90-day blanking period, trans-telephonic monitoring was conducted weekly through 21 weeks, and monthly thereafter. Continuous 48-hour Holter monitoring was also performed at 6 and 12 months. Of the 35 patients who received the PULSE3 waveform, 16 (mean age 58.1 years, 71 percent male) completed the 12-month follow-up.

Safe and efficacious

Acute isolation was achieved in 100 percent of pulmonary veins using 3.9 waveform applications per vein in the total cohort. In the PULSE3 cohort, 100 percent acute pulmonary vein isolation was achieved using 4.8 applications per vein. [Reddy V, et al, EHRA 2024]

The transpired ablation time or the time from the beginning of the first lesion to the end of the last lesion was approximately 10 minutes (total cohort: 10.0 min; PULSE3: 10.6 min), while the total left atrial dwell time with the catheter was around 20 minutes (total cohort: 19.1 min; PULSE3: 22.3 min), Reddy said. The total procedure lasted roughly an hour (total cohort: 56.5 min; PULSE3: 59.3 min), and the total fluoroscopy time was 6 minutes (total cohort: 5.7 min; PULSE3: 6.1 min).

On invasion mapping, 12-month freedom from atrial arrhythmia recurrence was documented in 81.8 percent of patients in the total cohort and in 100 percent in the PULSE3 subgroup.

There were no device- or procedure-related adverse events recorded, Reddy said. There was one patient who had diplopia and vertigo that lasted for 2 days, which the investigators deemed to be a migraine-like phenomenon seen after ablation procedures. Esophageal observations in a subset of patients (n=18) showed no evidence of thermal injuries. In brain MRI findings, four out of 40 patients (10 percent) had diffusion-weighted imaging–positive/T2-FLAIR–positive events.

Finally, in terms of pulmonary vein durability, progressive improvements were achieved from PULSE1 through PULSE3 both on a per-vein basis (82 percent, 88 percent, and 99 percent) and on a per-patient basis (61 percent, 67 percent, and 96 percent).

“In this first-in-human study, we conclude that the conformable pulsed-field ablation catheter was efficient, safe, and clinically effective for performing pulmonary vein isolation. And it creates durable pulmonary vein isolation lesions, at least with the final wave form,” Reddy said.

The study had a relatively small number of operators, centres, and patients, Reddy acknowledged. The data were based on intermittent rather than continuous monitoring, and “it’s likely that we are overestimating the success.”

Also, the utility of the catheter has yet to be established for other lesion sets and populations, he added.