There has been great excitement about pulsed field ablation (PFA) in the field of EP since the first publication utilizing PFA for paroxysmal atrial fibrillation (AF) in humans showing efficacy, safety, and durability of the new energy delivery system [1]. The same group analyzed feasibility of adjunctive posterior wall isolation (PWI) in persistent AF patients, with invasive re-mapping at 2–3-month period—it demonstrated 96% PVI and 100% PWI durability [2]. They additionally explored the long-term outcomes of PFA in paroxysmal AF patients and reported that about three-quarters of them remained atrial arrhythmia-free at 49 ± 7 months while no long-term complication was observed [3]. There was also a multinational effort to collect and analyze data for patients who underwent PFA for both paroxysmal and persistent AF [4]. MANIFEST-PF analyzed 1568 patients, and freedom from clinical atrial arrhythmia reached 78.1% at 1 year, while major adverse events occurred in 1.9% of the cases, with more than half being cardiac tamponade. Esophageal fistula and symptomatic pulmonary vein stenosis did not occur, and there was one case (0.06%) of persistent phrenic nerve injury.

Unlike traditional thermal energy leading to indiscriminate destruction of the surrounding structure, PFA utilizes electroporation causing relatively myocyte-specific irreversible lysis of cellular membranes while leaving other types of tissues intact. The concept of PFA was exciting in several ways: (1) each application is short and wide (depending on catheter design) so PVI can be achieved much faster than radiofrequency, (2) the most feared complications from thermal energy including atrio-esophageal fistula, phrenic nerve injury, and pulmonary vein stenosis are less likely to occur, and (3) PFA, when optimized, may lead to more durable lesions than from thermal energy given irreversible cellular lysis. The most commonly used PFA system in this current state of literature is FARAPULSE system (Boston Scientific, Marlborough, MA), but many different systems have been developed including Sphere-9 (Medtronic Inc, Minneapolis, MN), VARIPULSE (Johnson & Johnson, New Brunswick, NJ), and PulseSelect (Medtronic Inc, Minneapolis, MN). With the development of these PFA catheters, the million-dollar question remains: Is PFA better than our traditional tools? A recent randomized, single-blind, noninferiority trial was performed to address this question by comparing PFA vs conventional thermal ablation in patients with paroxysmal AF [5]. This trial demonstrated that PFA is non-inferior to thermal energy in efficacy (treatment success at 1 year: 73.3% in PFA vs 71.3% in thermal ablation) and safety (serious adverse event 2% in PFA vs 1.3% in thermal ablation).

In this issue of Journal of Interventional Cardiac Electrophysiology, the study by Maurhofer et al.’s group carried out a propensity score matched analysis to compare procedural characteristics, safety, and efficacy of each ablation strategy (PFA vs radiofrequency ablation (RFA) vs cryoballoon ablation (CBA). The group followed each patient with a 7-day Holter at 3-, 6, and 12-months post ablation, and freedom from recurrence of atrial tachyarrhythmia was the highest in the PFA group (85%) compared to RFA (73.8%) or CBA group (66.2%). Although it was not statistically significant, there appeared to be numerical trend towards superiority of PFA. The group presents an interesting complication of 2 cases (5%) that resulted in pericardial tamponade, and this was thought to be from an RV catheter which was later avoided. As expected, RFA had longer procedural time and lower fluoroscopy dose while PFA and CBA had shorter procedural time at the cost of higher fluoroscopy dose. Patients who underwent PFA had significantly longer waiting time to ablation since initial AF diagnosis (PFA 29 months vs RFA 11.5 months vs CBA 17 months). This may reflect patient selection bias for those who wanted PFA or the nature of availability of the technology. Overall, this study demonstrated confirmatory finding that efficacy of PFA is similar to thermal ablation with a hint of superiority of PFA.

With that in mind, is PFA truly good as it sounds? So far, while none of the published trials aimed to test superiority, numerous studies have shown that its efficacy and safety are similar to other ablation modalities. We have much more history and familiarity with thermal ablation with day-to-day usage, and numerous strategies have been developed to mitigate the potential complications of thermal energy by monitoring esophageal temperature, pacing phrenic nerves, and defining pulmonary vein antra. Rather, some complications, especially cardiac tamponade, seem to be numerically higher with PFA, possibly due to the use of a new technology with a larger and stiffer catheter and/or use of an RV catheter during PFA delivery.

It is clear that PVI alone is not enough to prevent atrial tachyarrhythmia with recurrence in about one out of four patients. Historically, it has been debated whether PWI adds to improved efficacy. In practice, PWI is certainly considered in persistent AF or posterior wall scar. The most common limitation of successful and durable PWI is due to esophageal heating with RFA, and it is common to see re-connection or atypical flutter using the posterior wall as the critical isthmus point due to incomplete ablation. A recent study compared hybrid epicardial/endocardial ablation vs endocardial only ablation in long-standing persistent AF patients [6]. The hybrid approach achieved PWI via epicardial approach whereas endocardial-only approach involved roof line without PWI. Expectedly, with long-standing persistent AF overall efficacy was modest, but with complete PWI through epicardial approach, freedom from atrial tachyarrhythmia was significantly higher (65.8% vs 37%). This suggests that complete PWI without concern for esophageal heating led to much higher efficacy in this population. Similarly, PFA will likely play a critical role in durable and complete PWI without concern for esophageal heating.

While PFA is rapidly evolving, whether it will truly take over the field of EP or remain as simply an option is currently unclear. For some providers, if efficacy is similar to traditional thermal ablation, shorter procedure time may be a good enough reason to switch over. For others, no fluoroscopy in RFA cases and familiarity with traditional thermal energy may be more desirable. Further, longitudinal data on efficacy and safety will be needed to better guide our decision.