Pulsed-Field Ablation for Atrial Fibrillation ― Achieving Excellence With a Simplified Technique ―
論文ID: CJ-23-0596
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論文ID: CJ-23-0596
Since the development of catheter ablation for atrial fibrillation (AF), pulmonary vein isolation (PVI) has remained the cornerstone of this therapeutic approach. Various technical advancements, including the use of different energy sources, have ensured the safety, efficacy, and simplicity of PVI. Today, radiofrequency catheter ablation (RFCA) and cryoballoon ablation (CBA) are the commonly used techniques.1
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Pulsed-field ablation (PFA) is emerging as a prominent energy source for AF ablation.2–4 Through continuous application of a direct current with a brief pulse width over a short period, an electrical field is established in the cells, leading to the formation of small pores in cell membranes, a process termed “electroporation”. If the pores created in the cellular membrane are small or limited in number, only a transient increase in membrane permeability occurs, known as “reversible electroporation” (RE). However, when the size of the membrane pores becomes irreparable, the cell dies, which is known as “irreversible electroporation” (IRE). Notably, cardiomyocytes exhibit a lower threshold for IRE than other cell types, including vascular smooth muscle cells, endothelial cells, nerve cells, and fibroblasts. Given the appropriate voltage, pulse width, and frequency when performing PFA, cardiomyocytes undergo IRE, while the surrounding tissue cells experience RE and survive, making it possible to selectively ablate the myocardium.
There are several clear advantages exist for PFA compared with traditional thermal ablation.
• Safety: PFA allows the ablation of cardiomyocytes with high tissue selectivity. Furthermore, no heat is generated when PFA is administered under proper settings. This ensures that PVI in AF ablation can be achieved without collateral damage such as atrioesophageal fistulas and phrenic nerve paralysis.
• Simplicity: all commercially available or clinically tested PFA catheters have been developed as one-shot devices for PVI, delivering a single packet of energy in seconds. Unlike thermal ablation, tissue contact is not mandatory, which simplifies the procedure.
• Efficacy: with the high tissue selectivity of PFA and proper protocols that ensure sufficient PF strength, PFA can easily achieve durable PVI.
• Efficiency: isolation of a PV can be accomplished with several packets of PFA application, dramatically reducing the time required for PVI.
These features are expected to significantly improve the quality of AF ablation by making it easier to achieve a safe and durable PVI in less time and are expected to have a significant effect on the AF ablation market as a “game changer.” Even in preliminary studies, impressive safety profiles and comparatively favorable outcomes have been reported.5–8
Today, the efficacy of additional ablation beyond PVI, including empirical linear ablation, posterior wall isolation, low-voltage area ablation, and defragmentation, is not necessarily well established.9 Therefore, especially for initial ablations in cases of early-stage AF, performing the procedure with the simplest protocol (i.e., focusing on efficient PVI alone while ensuring safety and efficacy) is a valid and reasonable treatment strategy. Given its characteristics, PFA has the distinct advantage of facilitating procedures with its simpler setting and protocol than RFCA or CBA (Table).
| RFCA | CBA | PFA | Features of PFA | |
|---|---|---|---|---|
| Necessity of catheter–tissue contact for ablation |
Essential | Essential | Desirable | Ablation without tissue contact can be achieved with a sufficiently strong pulse field |
| Comparative technical difficulty for PVI |
Moderate | Mild | Minimal | The procedure is more straightforward because ablation without tissue contact is achievable |
| Feasibility of 1-shot PV isolation | No | Yes | Yes | Currently, the PFA catheter is designed as a one-shot device |
| Comparative duration required for PVI |
Longer | Medium | Shorter | PV can be isolated with just a few applications of PFA for several seconds per packet |
| Necessity of 3-dimensional mapping systems |
Crucial | Optional | Optional | A straightforward procedure reduces the need for such systems |
| Sufficient PV potential detection by ablation catheter |
No | Yes | Yes | This feature contributes to the simplifying of the procedure |
| Feasibility of extra-PV ablation | Yes | Partially | Partially | The PFA catheter has a form suitable for PVI and should be used for initial treatments |
| Feasibility of durable PVI | Depends | Yes | Probable | Probably durable, but the outcome might vary depending on the PFA system used |
| Myocardium-selective ablation | No | No | Yes | A key feature of PFA |
| Risk of permanent phrenic nerve injury |
Yes | Yes | No | This contributes to the safety and simplification of the procedure |
| Is phrenic nerve pacing routinely required? |
No | Yes | No | |
| Risk of esophageal injury | Yes | Yes | No | This contributes to the safety and simplification of the procedure |
| Is esophageal temperature monitoring recommended? |
Yes | Yes | No | |
| Risk of PV stenosis | Yes | Yes | No | This contributes to the safety of the procedure |
AF, atrial fibrillation; CBA, cryoballoon ablation; PFA, pulse-field ablation; PV, pulmonary vein; PVI, PV isolation; RFCA, radiofrequency catheter ablation.
Until recently, the pentaspline PFA catheter manufactured by Boston Scientific alone was clinically available and approved as an insured treatment only in Europe. However, PFA is expected to become available in other countries in the coming years, and insights gained from the European clinical experience will be valuable for AF ablation practitioners worldwide.
In this issue of the Journal, Tilz et al propose a simplified PFA treatment protocol based on their experience using the pentaspline PFA catheter. It is characterized by (1) a single venous puncture of the femoral vein guided by ultrasound, (2) a single transseptal puncture, (3) single-catheter PVI, and (4) hemostasis using a venous closure system.10
Typically, during AF ablation, multi-electrode catheters are inserted into the heart for backup pacing, mapping of non-PV foci or concomitant atrial tachyarrhythmias, and recording PV potentials during RFCA. The authors10 decided to focus exclusively on PVI during the initial sessions and deliberately avoided other interventions. This approach enabled the adoption of a protocol that utilizes a single venous puncture. Transient bradycardia, which can occur during ablation, was managed by administering atropine sulfate beforehand. In Germany, the use of intracardiac echocardiography (ICE) during transseptal puncture is not widespread due to cost concerns, leading physicians to become proficient in performing this procedure under fluoroscopic guidance, which contributes to the feasibility of a single venous puncture using this protocol.
In this study of 50 patients,10 PVI was successfully achieved without touch-up in all cases. The average procedure duration was only 27.4±6.6 min. and complications were minimal, with transient phrenic nerve paralysis (n=2) and minor bleeding at the puncture site (n=2) being the only issues. Although it was inadequate for assessing efficacy, because of the limited follow-up period, the protocol appears very promising in terms of safety and efficiency.
The same group have also conducted similar research using very-high-power short-duration RFCA (90 W × 4 s) for PVI and compared it with conventional high-frequency ablation settings (up to 50 W).11 As a result of procedures performed by 2 highly experienced operators, procedure durations were 59±13 min and 101±38 min, respectively. Both procedures involved 3 femoral vein punctures, highlighting the efficiency and simplicity of the current protocol.
The 5S study is renowned for its research using PFA.12 The procedure duration in the latter phase of that study was 38±14 min. That approach involved 2 punctures in the femoral vein, and in some cases, an esophageal temperature sensor was used. The current report10 pertains to more recent cases, suggesting possible advancements in the techniques, which may account for the variance in procedure duration. The 5S study provides a more detailed report of the use of a PFA catheter during treatment, including safety findings from magnetic resonance imaging of the brain and endoscopic views of the esophagus, as well as efficacy regarding recurrence rates. Conversely, the present report emphasizes simplification of the entire treatment process, as well as proposing methods for puncture and hemostasis, which gives a more comprehensive perspective. Such an encompassing viewpoint would be valuable for physicians worldwide who are venturing into PFA.
The protocol proposed by Tilz et al10 is the simplest standard for PFA-based PVI. Depending on the practitioner’s experience and skills, as well as the specific conditions of the region where the treatment is conducted, it may be desirable to modify this protocol. For instance, incorporating ICE or electrode catheters into the protocol may be advisable.
