Pulsed field ablation (PFA) has gained increasing traction as a viable tool for treating cardiac arrhythmias, especially over the past few years. Qualities that have made PFA attractive as a therapeutic modality include the relative enhanced sensitivity of cardiomyocytes compared to other cell types and the apparent lack of significant thermal effects, both of which may reduce the risk of collateral damage to neighboring structures [1]. PFA-based catheters have been designed and tested primarily in the context of atrial arrhythmias [2, 3], with several systems already being clinically used in Europe. By contrast, exploration of ventricular ablation with PFA has been largely confined to animal studies thus far [4, 5]. Expansion to the ventricle opens up major advantages to treat originating arrhythmias which could be revolutionary.

In this issue of the journal, a preclinical investigation [6] by Aryana and colleagues reported on the performance of a novel PFA-based system which utilized linear and spiral catheter designs. Twenty ventricular endocardial and epicardial lesions were delivered in ten healthy swine, seven of which survived for 14–28 days to show sustained lesion formation. Notably, there were significant reductions in electrograms post-PFA, and these electrical changes persisted on end-study electroanatomic voltage mapping. This correlated with lesion formation noted on histopathology; although lesion distribution varied depending on the catheter size/shape used, lesion depth was similar across the three designs—approximately 8 or 9 mm. No evidence of permanent damage to adjacent structures such as coronary arteries or phrenic nerve was noted, nor was there char (suggestive of lack of thermal effect) or thrombus noted. Apart from movement due to phrenic nerve capture, PFA deliveries did not lead to significant skeletal muscle stimulation as measured by a smartphone-based accelerometer.

The authors are to be congratulated for their efforts in elucidating the effects of PFA on ventricular myocardium using their ablation system and catheter form factors. Atrial and ventricular tissue differ in several ways, notably tissue thickness and cellular composition as well as their surrounding milieu [4]. Hence, what works well for atrial ablations may not necessarily hold true in the ventricle. The experiments performed by Aryana et al. provide compelling evidence that large and durable lesions can be created in the ventricular myocardium with the tested catheters and delivery parameters used. The histopathological studies also provide reassurance that key structures such as the coronary arteries and phrenic nerve could be “spared” with PFA even when administered in close proximity. The bipolar/biphasic configuration appears to minimize skeletal muscle stimulation, which is an important factor from a patient comfort and safety perspective, as well as potential procedural benefit such as avoiding the need for general anesthesia. Finally, QRS gating as utilized by other PFA systems will likely be key in avoiding iatrogenic induction of ventricular fibrillation if energy is delivered in the vulnerable period.

Despite these promising findings, several questions remain unanswered. Although some degree of lesion depth penetration was seen, it is unclear if this will be sufficient for a deep intramyocardial substrate [5]. Its use in ventricular tachycardia involving the interventricular septum or left ventricular summit—both highly relevant and challenging scenarios in our field—therefore is unclear. Similarly, the lesions created are in healthy swine myocardium, and how the presence of scar/fibrosis affects lesion size/depth will need to and should be evaluated in follow-up studies. Furthermore, coronary artery spasm in association with PFA delivery has been reported and will likely be a relevant and persistent clinical concern [7, 8]; such data was not assessed or at least reported on in the present study. Although the spiral catheter design is clearly appropriate for tubular structures like the pulmonary veins, its utility in ventricular ablations seems more equivocal, and similar designs have led to entrapment in the mitral valve apparatus. However, this was not seen in this study. Finally, as with most other PFA manufacturers, few details regarding the delivery parameters have been made public, which continues to impede our understanding of PFA as a community. This is despite the current assumption that the optimal recipe for energy delivery is inherently different for each unique system and catheter design, which produces unique electric fields at the catheter-tissue interface.

Catheter ablation for ventricular tachycardia is a prominent challenge in the realm of electrophysiology; hence, innovations in ventricular PFA as shared by the authors are a much-needed step in the right direction. With that being said, we encourage all investigators to become more transparent with the specific parameters tested with their respective PFA systems, as this will help to foster greater advancement and growth for the betterment of our patients and accelerate the field towards realizing PFA for ventricular arrhythmias such as ventricular tachycardia and perhaps even ventricular fibrillation.