When Will Pulsed Field Ablation Replace Radiofrequency Ablation for Cavotricuspid Isthmus-Dependent Atrial Flutter?

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 EP LAB DIGEST. 2025;25(8):6.

Bradley P Knight, MD, FACC, FHRS

Dear Readers,
Pulsed field ablation (PFA) has quickly become the preferred energy source for catheter ablation in patients with atrial fibrillation (AF) undergoing pulmonary vein isolation (PVI). There are now 4 commercially available PFA systems in the United States. Each tool has a different form factor and electrical waveform, but are all very effective at safely and efficiently achieving PVI. Although not specifically designed to ablate atrial flutter (AFL), these same catheters can also be used to ablate the cavotricuspid isthmus (CTI) in patients with a history of typical AFL during the same procedure after PVI has been achieved. For now, the PFA catheters are too expensive and unnecessary for routine stand-alone CTI ablation.

The circular, multi-electrode, over-the-wire PulseSelect PFA catheter (Medtronic) can be placed in a linear fashion along the CTI either with all the electrodes exposed or with some of the proximal electrodes pulled into, and covered by, the deflectable sheath. The pentaspline Farapulse PFA catheter (Boston Scientific) can be used to deliver PFA to the CTI using either a flower or basket form configuration. When this catheter is in a flower configuration, its large diameter makes it difficult to place directly onto the CTI, but with experience, it can be commonly achieved. Some physicians have creatively used this catheter while over-the-wire by retracting some of the proximal electrodes into the deflectable sheath to make a small distal basket shape. The 9-mm mesh-like Sphere-9, dual-energy, Affera PFA catheter (Medtronic) can readily be used to deliver PF or radiofrequency (RF) energy to the CTI, and unlike the other catheters, it is approved by the United States’ Food and Drug Administration for CTI ablation. Ablation of the CTI has also been described using the most recently approved, variable loop VARIPULSE PFA catheter (Johnson & Johnson MedTech).

Using PFA rather than RF to ablate the CTI is appealing because PFA is faster, less reliant on sustained contact force, and less dependent on the anatomy and length of the CTI. However, it has been recognized from early experience that delivering PFA near the coronary arteries can cause coronary artery spasm. This must be accounted for when ablating the CTI near the right coronary artery, or the lateral mitral isthmus near the left circumflex artery. High-dose intravenous nitroglycerin is used by many physicians when using some of the PFA catheters to ablate the CTI to minimize the risk of coronary spasm, but does not eliminate the risk. Some preliminary data also suggest that PFA adjacent to a coronary artery can cause undesirable, long-term intimal hyperplasia of the vessel wall. Dual-energy PF/RF catheters offer the flexibility to selectively use RF near the annulus and PF on the way back to the inferior vena cava. PFA catheters can also create large lesions that could create heart block when ablating the septal aspect of the CTI.

In July 2025, a European team prospectively studied the use of a focal monopolar PFA ablation catheter (CardioFocus) to ablate the CTI in 82 patients with typical AFL.¹ They compared their results to those from 27 patients who underwent CTI ablation using standard RF. A majority of patients were undergoing a concomitant PVI and CTI ablation. For PFA, the proportion of first-pass CTI block was markedly higher at 93% compared to 55%, and the CTI ablation procedure times were 10 minutes shorter (7 minutes versus 17 minutes). Importantly, however, 5% of patients in the PFA group developed transient ST elevation, despite administration of nitroglycerin, and 2% showed transient complete heart block during ablation. Although no patients developed persistent complete heart block, there was a small but significant number of patients who had persistent PR prolongation during long-term follow-up.

The days of using RF to perform point-by-point ablation of the CTI are numbered, even when performed as a stand-alone procedure. At some point, companies will develop affordable catheters dedicated to ablation of the CTI that can also avoid coronary spasm and minimize the pain associated with skeletal muscle capture. At that point, only PFA or dual-energy PF/RF catheters will be used to ablate typical AFL. That will be a welcome advance. 

Disclosures: Dr Knight has served as a paid consultant to Medtronic and was an investigator in the PULSED AF trial. In addition, he has served as a consultant, speaker, investigator, and/or has received EP fellowship grant support from Abbott, AltaThera, AtriCure, Baylis Medical, Biosense Webster, Biotronik, Boston Scientific, CVRx, Philips, and Sanofi; he has no equity or ownership in any of these companies. Dr Knight reports payment or honoraria from Convatec for a lecture. 

Reference

1.    Farnir FIP, Chaldoupi S-M, Hermans B, et al. Ablation of cavo-tricuspid isthmus dependent atrial flutter using a focal monopolar pulsed-field ablation catheter: feasibility, periprocedural coronary spasms and conduction disorders. Heart Rhythm. 2025 Jul 4:S1547-5271(25)02630-X. Online ahead of print. doi:10.1016/j.hrthm.2025.07.001