麻豆传媒

During pulsed field ablation (PFA) for atrial fibrillation (Afib or AF), the additional creation of mitral isthmus ablation lines often led to vasospasm of the neighboring left circumflex artery, early data suggested.

Coronary artery vasospasm was provoked in 41.2% of Farapulse PFA procedures at the posterolateral mitral isthmus, according to a small case series from Homolka Hospital in Prague that was reported by Vivek Reddy, MD, of Icahn School of Medicine at Mount Sinai in New York City, and colleagues.

Notably, instances of spasm reached 77.8% when the ablation line was situated superiorly along the mitral isthmus -- yet did not happen in any of the eight cases where the line was situated inferiorly.

Coronary spasms did not occur in any of the nine patients undergoing more conventional radiofrequency ablations (RFAs). Of another five RFA patients who failed to achieve conduction block and crossed over to PFA, coronary spasm occurred in three: two mild cases and one self-resolving severe case, the study authors reported in .

They noted that 90% of spasms were subclinical -- no ST-segment elevation, arrhythmias, or ventricular wall motion abnormalities -- with the remaining 20% requiring nitroglycerin administration. There was one instance of dynamic ST-segment changes without hemodynamic instability. The median time to remission was 5 minutes.

Durable bidirectional conduction block is the goal during for treating Afib that is refractory to pulmonary vein (PV) isolation or a re-entrant, mitral isthmus-dependent left atrial flutter. In this report, PFA at the mitral isthmus achieved bidirectional conduction block in all 17 patients, with an average 10.5 pulsed field applications per patient.

Reddy's group had previously reported frequent coronary spasm during PFA of the cavotricuspid isthmus (CTI) -- another adjunctive procedure for atrial flutter that can be performed during catheter ablation.

"The high efficacy of PFA for ablation of the mitral isthmus in this study is encouraging, and these findings suggest that PFA of the mitral isthmus is less likely to cause coronary spasm compared with ablation of the CTI, especially when the ablation is performed inferiorly," commented Bradley Knight, MD, and Anna Pfenniger, MD, PhD, both from Northwestern University in Chicago, in .

PFA uses a novel energy modality relying on very brief, high-voltage electric pulses, in contrast to conventional thermal ablation. The concept takes advantage of myocardial cells having the lowest thresholds to electric fields to preferentially ablate myocardial tissue, without injuring nearby tissues.

This year, the PULSED-AF trial showed that the PulseSelect PFA system exceeded safety and effectiveness targets for PV isolation.

More recently, the Farapulse/Farawave PFA system showed noninferiority over thermal ablation in treating paroxysmal Afib in the ADVENT trial. Separately, other data suggest that the clinical benefits and safety of Farapulse PFA apply to men and women alike in real-world practice in Europe.

"Although some might challenge the need to adopt PFA in the absence of demonstrable superiority, the shorter procedure times, the ability to efficiently perform not just PV isolation but ablation of the entire posterior left atrium for patients with persistent AF, and the avoidance of rare but feared complications related to collateral injury will likely drive adoption of the technology even if trial data show similar efficacy," Knight and Pfenniger predicted.

"Despite the continued faith that PFA will be a better energy source for AF ablation compared with radiofrequency and cryoenergy, many concerns such as the durability of lesions and the creation of coronary vasospasm remain," the editorialists nevertheless wrote.

Crucial questions include how exactly PFA can induce coronary spasm, how these spasms can be reliably avoided, and what the long-term sequelae of spasm are.

"While not studied here, we previously demonstrated that nitroglycerin pretreatment during PFA at the CTI eliminated severe vasospasm. This is consistent with spasm resulting from temporary membrane permeabilization of smooth muscle, local release of calcium or inflammatory mediators, or stimulation of ganglionated plexi causing autonomic imbalance," Reddy's group noted. "Additional studies should assess whether routine prophylactic nitroglycerin pre-PFA is superior to expectant administration only when vasospasm occurs."

In the present report, operators performed systematic coronary angiography during catheter ablation at the posterolateral mitral isthmus to assess the frequency and severity of vasospasm of the adjacent left circumflex artery. IV nitroglycerin 1 mg was planned for spasm persisting beyond 20 minutes or for significant ST-segment changes.

The prospective cohort study covered 26 consecutive adult patients receiving first-ever PFA (n=17) or RFA (n=9) of the mitral isthmus during catheter ablation of Afib in 2022 at a single center. This was a group with 73% men and a mean age of 65.5 years. Persistent Afib was observed in 69%.

PV isolation was successful in all PVs in 24 patients with PFA and two patients with RFA.

RFA of the mitral isthmus was always situated superiorly and resulted in bidirectional block in four out of nine patients -- even after 20.7 lesions per patient on average -- the remaining five having to resort to PFA.

Reddy and colleagues cautioned that their report was only based on one Farawave PFA catheter, so their findings may not be generalizable to other devices.

Several PFA systems are already commercially available in Europe, and two are expected to be FDA approved in the next year, according to Knight and Pfenniger.

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