NATIONAL HARBOR, MD. – Cardiac electrophysiologists have reported using pulsed field ablation, a new power source for catheter ablation of atrial fibrillation, on fewer than 150 patients worldwide in initial clinical studies, but its performance so far and the promise it carries for substantially improving the safety and efficacy of catheter ablation has convinced many experts that it represents the future for this intervention.
Dr. Andrea Natale
“I’m very excited about PFA [pulsed field ablation]. It may make everything else obsolete,” Andrea Natale, MD, said at the annual International AF Symposium. “We need to see more efficacy data, but just for safety alone there is no reason to use anything else,” commented Dr. Natale, executive medical director of the Texas Cardiac Arrhythmia Institute at St. David’s Medical Center in Austin,Tex.
“The main issue is safety, and if PFA lives up to its promise, then [using it preferentially] is not a difficult decision,” commented Francis E. Marchlinski, MD, professor of medicine and director of electrophysiology at the University of Pennsylvania.
Dr. Francis Marchlinski
“The only question is whether it has good long-term efficacy” because so far no patients have been followed for longer than about a year after PFA treatment, noted Moussa Mansour, MD, director of the cardiac electrophysiology laboratory at Massachusetts General Hospital in Boston. “If that piece turns out to be true, then I think it will be a winner.”
Vivek Y. Reddy, MD, one of the few investigators to have already collaborated on clinical studies that used PFA to catheter ablate both in patients with paroxysmal and, more recently, persistent atrial fibrillation (AFib), put it this way: “I’m 99% sure” PFA will be the energy of choice in the near future for AFib catheter ablation. The 1% of uncertainty “is only because of what might be unknown, something we’re not expecting,” said Dr. Reddy, professor of medicine and director of the cardiac arrhythmia service at Mount Sinai Medical Center in New York.
Dr. Moussa Mansour
He and his associates at a center in Prague and at a second site in Bordeaux, France, reported their collective experience in 2019 regarding use of PFA on 81 patients with symptomatic, paroxysmal AFib who had not responded to at least one antiarrhythmic drug (J Am Coll Cardiol. 2019 Jul;74[3]:315-26). During a session on PFA at the symposium, Pierre Jaïs, MD, a cardiac electrophysiologist and professor of cardiology at the University of Bordeaux, updated this experience to now include 113 patients treated by the end of 2019 at the same two centers plus now an added third site, an experience accumulated by a total of five operators. Fifty-one patients have now been followed for at least a year, with no “unexpected” safety events, said Dr. Jaïs, The most recent 88 patients underwent PFA without general anesthesia. The ablation technique has undergone several refinements during this experience, and with use of the most recent, biphasic protocol that’s so far treated 26 patients, 24 (92%) of the treated patients had no reconnected AFib circuits in their atrial tissue when they underwent remapping 3 months after their procedure.
Dr. Vivek Y. Reddy
Magnetic resonance imaging of the left atria of these patients after pulmonary vein isolation with PFA showed a uniquely homogeneous and continuous lesion that functionally isolated each vein from surrounding atrial tissue and denoted a more uniform and complete ablation, Dr. Jaïs noted. “I have never seen [an ablation] as homogeneous.” The Magnetic resonance pictures also showed that the esophagus in each treated patient remained completely undamaged. “Esophageal sparing is systematically observed,” along with phrenic nerve sparing that’s in notable contrast with what’s seen with conventional energy sources, he said. The images also indicated that edema was substantially reduced compared with both radiofrequency and cryoablation, while mechanical function of treated left atria has consistently been “well preserved.”
“For the first time, we can use extra power to ensure durable lesions without compromising safety,” Dr. Jaïs concluded. PFA appears to put AFib ablation “on the verge of a totally new era.”
Dr. Pierre Jais
The less extensive and briefer experience in patients with persistent AFib has been completely consistent. This included 25 patients who had not responded to at least one antiarrhythmic drug treated by either of two operators, one in Prague and the other in Split, Croatia. All 25 patients who underwent pulmonary vein isolation had the procedure successfully completed as assessed with acute mapping of arrhythmia circuits after ablation, and the 24 of these patients who also underwent posterior wall ablation with the PFA device all had a successful acute result according to mapping, Dr. Reddy reported. No patient had an adverse event. PFA treatments were relatively fast, with an average procedure time in this series of 132 minutes. Repeat mapping 3 months after treatment is still pending.
At the heart of PFA’s safety is its “myocardial selectivity” which has so far kept PFA from causing any esophageal or phrenic nerve injuries, two potential complications of conventional AFib catheter ablation with use of either radiofrequency or cryo energy. Dr. Reddy was quick to highlight that there is no absolute selectivity for myocardium. “If you create a big enough field, it will electroporate everything, but the margin [between safety and damage] seems wide enough to take advantage” of focally damaging myocardial tissue in the left atrium to disrupt arrhythmia circuits while sparing adjacent tissue. Irreversible electroporation is the means by which PFA destroys targets cells while leaving other tissue unscathed, and a precisely adjusted PFA signal can focus its lethal effect exclusively on myocardial cells, a feature of PFA that Dr. Reddy called “lucky.”
The pulsed field ablation studies have been sponsored by Farapulse, the company developing this device, which in May 2019 received breakthrough designation for priority review from the Food and Drug Administration.
Dr. Reddy and Dr. Jaïs are both consultants to and shareholders in Farapulse. Dr. Natale has received honoraria from or has been a consultant to Biotronik, Janssen, Medtronic, and St. Jude. Dr. Marchlinski has been a consultant to or has received honoraria from Abbott EP/St. Jude, Biotronik, and Medtronic. Dr. Mansour has been a consultant for Abbott and Medtronic, has an equity interest or stock options in NewPace and EPD Solutions, and has received research grants from Abbott, Boehringer Ingelheim, Pfizer, and Sentre Heart. In addition, all sources have received consulting fees, honoraria, and/or research grants from Biosense Webster and Boston Scientific.