Novel Pulsed Field Ablation System Turns to High-Energy, Ultra-Short Zaps

The future of pulsed field ablation (PFA) technology could go in the direction of high-voltage nanosecond energy bursts, according to early results of a novel device.

With CellFX nsPFA-360 PFA for paroxysmal atrial fibrillation (Afib or AF), acute electrical isolation of all pulmonary veins (PVs) was achieved in 100% of cases in a 177-person first-in-human study from a group led by Vivek Reddy, MD, of Mount Sinai Fuster Heart Hospital in New York City.

The main safety result was a “reasonable” 1.7% incidence of device- or procedure-related serious adverse events: one each of inflammatory pericardial effusion, hemolysis with acute kidney injury, and stroke. Of note, there were no instances of phrenic nerve palsy, PV stenosis, esophageal complications, or death.

The study was presented at the annual Heart Rhythm Society meeting and its manuscript published in JACC: Clinical Electrophysiology.

Based on invasive remapping at 2-3 months, PV isolation (PVI) lesion durability reached 91% with 5-second applications with the CellFX system; this was notably better than the 79% durability seen with 2.5-second applications also tested. Additional nanosecond PFA was performed for incomplete lesions at this point.

“It is well accepted that achieving durable PVI is essential for enhancing long-term freedom from atrial arrhythmia recurrence. With the nsPFA catheter, we observed good PVI durability, both acutely and at 3-month invasive remapping, particularly when using 5-second pulses,” Reddy and colleagues wrote.

“The single-shot nsPFA catheter with all-in-one mapping and ablation capability can safely achieve durable lesions, translating to promising efficacy in paroxysmal AF,” they concluded.

The CellFX system comprises a compliant circular catheter with a pulsed field generator. The waveform produced is made up of nanosecond pulses up to 15kV in amplitude. These high-energy, ultra-short pulses should theoretically facilitate deeper lesions — therefore requiring fewer applications compared to the microsecond PFA systems currently on the market.

“This thermally-neutral, apoptosis-favoring mechanism — combined with the potential for a single-shot PVI-capable approach — may allow for high procedural efficiency, long-term durability, and good clinical effectiveness during AF ablation,” Reddy’s group wrote.

Study authors reported that in their study, 12-month freedom from atrial arrhythmia recurrence reached 86.5% overall — going up to 89.7% for those who got 5-second applications in particular.

The prospective single-arm study had 177 people with symptomatic paroxysmal Afib enrolled (age 61 on average, 36% women, mean left atrium 41 mm). Exclusion criteria were prior cardiac or surgical ablation, left ventricular ejection fraction <40%, and presence of an implantable cardioverter defibrillator or pacemaker, among others.

There were three participating European centers with seven highly experienced operators.

CellFX nanosecond PFA was delivered in 2.5- or 5-second applications, usually with one ostial and one antral lesion per vein, and guided by fluoroscopy and intracardiac echocardiography.

Some patients underwent additional ablation at the posterior wall (49%), cavotricuspid isthmus (6%), or mitral isthmus (16%) in addition to PVI.

Average total procedure and fluoroscopy times were 65 and 9 minutes, respectively.

All lesions were acutely successful, Reddy’s group found.

“It seems unlikely that such a high success rate could be the result of simply durable PVI. It is possible that the extra-PV lesion sets … may have contributed to success. But it is also possible that such an improved success could be related to extra-myocardial effects such as an impact on peri-atrial ganglionated plexi,” the investigators surmised.

“Indeed, while the impact of microsecond PFA on cardiac autonomic ganglia has been described to be mostly of acute or subacute impact, the autonomic effects of nanosecond PFA remain poorly understood and are the subject of ongoing research,” they noted.

Following the procedure, antiarrhythmic drugs and oral anticoagulation were continued as per standard of care. Of the 105 patients on class I/III antiarrhythmic drugs, 11 were still taking them at 12 months.

In a brain MRI substudy on 35 patients, rates of silent cerebral events/lesions were both 11.4% at 24-48 hours post-ablation — a “relatively low rate,” per study authors.

They acknowledged that they could have missed atrial arrhythmia recurrences in some patients due to the reliance on fairly short 24-hour continuous Holter monitoring and absence of frequent follow-up.

Results in this study may also not generalize to diverse operators in real practice, they cautioned, adding that they had also not sought data related to renal dysfunction.