Stiffness assessment of acute atrial lesions after radiofrequency and pulsed-field ablation using multifrequency magnetic resonance elastography

Abstract Background Extensive catheter ablation beyond pulmonary vein isolation may acutely increase atrial tissue stiffness, however, this may differ between energy sources used. Objectives This study aimed to compare acute effects of radiofrequency ablation (RFA) and pulsed field ablation (PFA) on atrial tissue stiffness in a porcine model using multifrequency magnetic resonance elastography (MMRE). Methods In 17 pigs (∼50 kg and ∼16 weeks old) an intercaval line was ablated using only focal RFA (25 W, 30 sec, n=9), only focal monopolar biphasic PFA (CENTAURI PFA generator, 25 A, 10 pulse trains, n=5), or half of the ablation line with PFA and the other half with RFA (n=3) (Figure 1,A). Post-ablation, in vitro MMRE data were acquired with a tabletop MRE scanner (ttMRE) (n=8) (Figure 1,B). In vivo, a novel MMRE protocol utilizing electrocardiography-triggered spin-echo, echo-planar-imaging was established (n=11) (Figure 1,C). Shear wave speed (SWS) was reconstructed as a surrogate for tissue stiffness. Results In vitro ttMRE measurements revealed significantly higher SWS for the RFA ablation zone compared to both the PFA ablation zone (p=0.008) and PFA border zone (p=0.003). Consistently, a novel in vivo MMRE protocol showed 1.37-fold higher SWS of the RFA ablation zone than its border zone (p=0.016) and 1.16-fold higher SWS than the PFA ablation zone (p=0.033). Absolute in vivo SWS differences between ablation zones and border zones were significantly higher for RFA compared to PFA (p=0.019). Conclusions RFA produces stiffer acute atrial lesions compared to PFA in pigs. A novel MMRE scanning protocol allows RFA and PFA lesion evaluation in vivo with the potential to support the refinement of future catheter approaches by optimizing mechanical properties of ablation lesions and minimizing atrial stiffness.