4.4 | The feasibility of MI block
In the Marshall-PLAN study by Derval et al,15 it was demonstrated that achieving a complete and durable MI block is crucial for improving atrial tachyarrhythmia-free survival in PeAF ablation. However, obtaining a complete MI block for RFCA is a challenge due to anatomical complexities such as tissue thickness, local blood flow, and epicardial musculature connections, including CS sleeves or a Marshall bundle.16 Additional techniques, such as ablation inside the CS and ethanol infusion into the vein of Marshall, are usually necessary. PFA is a nonthermal ablation method. The main challenge of MI block for PFA is tissue thickness and epicardial connections, excluding the temperature weakening of the blood flow.
A recent study proved MI block with PFA was successfully achieved in a high percentage (100%), but 2 patients developed severe coronary vasospasm of the circumflex artery.12 In our cohort, MI block was achieved in 81.3% of cases. The different success rates might be due to the different PFA catheter electrode configurations and energy waveforms from different manufacturers’ systems. We hypothesized that increasing electrode number, catheter contact surface area, application number, and energy output could improve the acute success rate of MI block, but bring about a higher risk of severe coronary vasospasm or severe haemolysis which was not observed in our study. Further studies with more cases are required to adjust the energy parameters and catheter electrode configuration to optimize efficacy and minimize procedural risks. Can focal PFA catheter ablation inside the CS damage the epicardial connections and bring about risks of coronary vasospasm, still needs further investigation. Both our study and the study by Baptiste Davong et al, PFA achieved a high success rate of acute MI block without ethanol infusion into the vein of Marshall or epicardial ablation in CS. Therefore, PFA could be a good alternative to obtain an MI block when RFCA fails, especially in cases without the vein of Marshal or the vein of Marshall cannot be catheterized. Thus, PFA could be recommended for perimitral left atrial flutter cases.