Pulsed field ablation prevents chronic atrial fibrotic changes and restrictive mechanics after catheter ablation for atrial fibrillation

Abstract

Aims: Pulsed field ablation (PFA), a non-thermal ablative modality, may show different effects on the myocardial tissue compared to thermal ablation. Thus, this study aimed to compare the left atrial (LA) structural and mechanical characteristics after PFA vs. thermal ablation.

Methods and results: Cardiac magnetic resonance was performed pre-ablation, acutely (<3 h), and 3 months post-ablation in 41 patients with paroxysmal atrial fibrillation (AF) undergoing pulmonary vein (PV) isolation with PFA (n = 18) or thermal ablation (n = 23, 16 radiofrequency ablations, 7 cryoablations). Late gadolinium enhancement (LGE), T2-weighted, and cine images were analysed. In the acute stage, LGE volume was 60% larger after PFA vs. thermal ablation (P < 0.001), and oedema on T2 imaging was 20% smaller (P = 0.002). Tissue changes were more homogeneous after PFA than after thermal ablation, with no sign of microvascular damage or intramural haemorrhage. In the chronic stage, the majority of acute LGE had disappeared after PFA, whereas most LGE persisted after thermal ablation. The maximum strain on PV antra, the LA expansion index, and LA active emptying fraction declined acutely after both PFA and thermal ablation but recovered at the chronic stage only with PFA.

Conclusion: Pulsed field ablation induces large acute LGE without microvascular damage or intramural haemorrhage. Most LGE lesions disappear in the chronic stage, suggesting a specific reparative process involving less chronic fibrosis. This process may contribute to a preserved tissue compliance and LA reservoir and booster pump functions.

Keywords: Atrial fibrillation; Atrial fibrosis; Cardiac magnetic resonance; Catheter ablation; Pulsed field ablation.

Graphical abstract

Figure 1

The burdens of acute and chronic late gadolinium-enhancement (LGE) and acute oedema. (A) Left atrial (LA) LGE lesions in acute and chronic stages. (B) LA oedema on hyper-T2 imaging in the acute stage. PFA, pulsed field ablation.

Figure 2

Examples of acute lesions on late gadolinium enhancement (LGE) and T2 imaging. (A–C) imaging after pulsed field ablation (PFA). (D–F) imaging after thermal ablation with radiofrequency energy. (A, D) maximum intensity projections of LGE volumes in anterior views. Acute LGE lesions were larger and more evenly distributed around pulmonary veins (PVs) after PFA (A) than after thermal ablation (D). (B, E) LGE images at the ostial level of the right superior PV. Acute LGE lesions after PFA (B) were more homogeneous than those after thermal ablation (E). Thermal ablation lesions showed dark areas within LGE (yellow arrows in E), consistent with intramural haemorrhage and/or microvascular damage. (C, F) Trans-axial T2 images showed oedema around PVs after both PFA (C) and thermal ablation (F), although slightly less after PFA.

Figure 3

Reversibility of late gadolinium enhancement (LGE) in the chronic stage. (A–D) LGE imaging after pulsed field ablation (PFA). (E–H) LGE imaging after thermal ablation with radiofrequency energy. (A, C, E, G) maximum intensity projections of LGE volumes in posterior views (A, E: acute; C, G: chronic). (B, D, F, H) LGE image series perpendicular to the axis of the right superior pulmonary vein (PV), displayed from antral to ostial level (B, F: acute; D, H: chronic). After PFA, the majority of acute LGE lesions (A, B) had disappeared in the chronic stage (C, D). In contrast, after thermal ablation, most acute LGE lesions (E, F) persisted in the chronic stage (G, H).

Figure 4

Maximum longitudinal strain values on the pulmonary vein (PV) antra. Changes in maximum longitudinal strain values in each patient of the pulsed field ablation (PFA) group and thermal group are shown.

Figure 5

Examples of strain measurements on the left pulmonary vein (PV) antra. Top row: patient treated with pulsed field ablation (PFA). Bottom row: patient treated with thermal ablation by using radiofrequency energy. Note that the endocardial border of the PV antra is traced in the cine image (left panels in both rows). In the acute stage, the maximum strain decreased in both patients. In the chronic stage, it recovered to the baseline level after PFA, whereas it remained low after thermal ablation.

Figure 6

Left atrial (LA) volume and function parameters. Changes in LA volume and function parameters in the pulsed field ablation (PFA) group (green boxes) and the thermal group (red boxes) are shown.