Catheter Ablation -> Atrial Fibrillation & Atrial Flutter: -> Experimental methods D-PO04 - Poster Session IV (ID 15) Poster

D-PO04-162 - Edema Formation During Cardiac Cryo-ablation (ID 476)

  E.G. Kholmovski: Honoraria/Speaking/Consulting Fee - MRI Interventions. Research (Contracted Grants for PIs and Named Investigators only) - Medtronic.


Background: Cryo-ablation is a well-established modality for AF treatment. Time course and extent of edema formation during cardiac cryo-ablation is poorly studied. Real-time MRI (RT-MRI) can be used to guide cryo-ablation procedure, assess freeze zone, and study edema formation.
Objective: To study edema formation during cryo-ablation.
Methods: Six RT-MRI guided cry-ablations of free wall of right ventricle (RV) were performed in 2 canines using MRI-compatible focal cryo-catheter and 3 Tesla MRI scanner. Validation of catheter tip-tissue contact and monitoring of freeze zone formation were performed by RT-MRI. T2-weighted (T2w) images were acquired prior to 4-minute freeze (baseline) and at multiple time points after ablation to assess edema formation. The earliest post-ablation T2w images were acquired 1-2 minutes after freeze to achieve tissue thaw. Wall thickness at ablation locations was measured on T2w images.
Results: Transmural lesions were delivered in all RT-MRI guided ablations. Edema formation was detected immediately (1.5-3 mins) after conclusion of 4-minute freeze (Fig. 1). Thickness of RV free wall at ablation locations increased drastically after freeze and continued to grow with time after freeze (Fig. 1). Wall thickness achieved the maximal value at 25-35 minutes after freeze. Darker core of edema region observed in later (> 10 minutes) T2w images indicates hemorrhage at freeze site (Fig. 1).
Conclusion: Edema starts to form immediately after cardiac cryo-ablation and continues to expand up-to 30 minutes after ablation. Edema significantly increases wall thickness at ablation site which may reduce efficiency of repeat freeze cycle performed at the same location.