Multimodal MRI-based assessment of atrial acute and chronic radiofrequency and pulsed field ablation lesions characteristics in a porcine model
K Jerltorp, K Wessels, M Noerregaard, L B H Friderichsen, B S Larsen, J Castelein, S M Chaldoupi, B J M Hermans, U Gang, J Hansen, N Vejlstrup, T Jespersen, S D Nissen, D LinzAbstract
Background
Catheter ablation is a cornerstone in the treatment of atrial fibrillation. While thermal energy sources, such as radiofrequency ablation (RFA), have conventionally been used in clinical practice, pulsed field ablation (PFA) is emerging as a novel non-thermal technique that is considered to demonstrate tissue-specific damage.
Objectives
This study aimed to compare the characteristics of acute and chronic ablation lesions in the right atria induced by RFA and PFA using cardiac Magnetic Resonance Imaging (MRI).
Methods
One intercaval line was ablated in 16 female Danish Landrace pigs (Baseline (BL); ~16 weeks old and mean weight 41 kg, follow-up (FU): 62 kg) using the same catheter, administering either focal RFA (Ampere RF generator, 25 W, 30 sec, n=8) or focal PFA (Cardiofocus CENTAURI PFA generator, 25 A, 10 pulse trains, n=8). Ablation lesions were assessed using cardiac MRI, specifically 3D T1-weighted gradient echo late gadolinium enhancement (LGE), non-contrast 3D T1-weighted long inversion time (TWILITE), and non-contrast 3D T2-weighted (T2w) sequences. BL imaging was performed directly after ablation, with additional FU imaging six weeks post-ablation to visualize chronic scarring. Lesion volume from the 3D LGE sequence was calculated based on a signal intensity ratio (SIR) of >1.1 for each voxel relative to the mean blood pool intensity of the right atrium.
Results
The T2w sequence visualized both acute RFA and PFA lesions, while the TWILITE sequence only visualized acute RFA but not PFA lesions (Figures 1 and 2). In the acute imaging, LGE and T2w imaging demonstrated that PFA lesions exhibited a greater volume compared to RFA lesions (RFA LGE BL mean:2.19 ±1.1 cm3, PFA LGE BL mean: 3.71 ±1.1 cm3, p=0.025, RFA T2w BL mean: 2.81±1.4 cm3, PFA T2w BL mean: 4.48±1.3 cm3, p=0.028). During the FU scans at six weeks, RFA and PFA lesions showed similar LGE, while T2w and TWILITE were negative. Furthermore, the FU scans revealed significant lesion shrinkage in both RFA and PFA groups, resulting in similar residual lesion volumes (RFA LGE FU mean: 0.60±0.8 cm3, PFA LGE FU mean: 0.73±0.8 cm3, p=0.59).
Conclusions
Distinct characteristics of RFA and PFA lesions during acute MRI suggest different acute lesion formation mechanisms before both types of lesions mature similarly with comparable MRI appearance after six weeks.