Real‐Time MRI‐Guided Cardiac Cryo‐Ablation: A Feasibility Study

Abstract

Introduction MRI based ablation provides an attractive capability of seeing ablation related tissue changes in real-time. Here we describe a real time MRI based cardiac cryo-ablation system. Methods Studies were performed in canine model (n=4) using MR-compatible cryo-ablation devices built for animal use: focal cryo-catheter with 8 mm tip and 28 mm diameter cryo-balloon. The main steps of MRI guided cardiac cryo-ablation procedure (real-time navigation, confirmation of tip–tissue contact, confirmation of vessel occlusion, real-time monitoring of a freeze zone formation, and intra-procedural assessment of lesions) were validated in a 3 Tesla clinical MRI scanner. Results The MRI compatible cryo devices were advanced to the right atrium (RA) and right ventricle (RV) and their position was confirmed by real-time MRI. Specifically, contact between catheter tip and myocardium and occlusion of superior vena cava (SVC) by the balloon was visually validated. Focal cryo lesions were created in the RV septum. Circumferential ablation of SVC-RA junction with no gaps was achieved using the cryo-balloon. Real-time visualization of freeze zone formation was achieved in all studies when lesions were successfully created. The ablations and presence of collateral damage were confirmed by T1-weighted and late gadolinium enhancement MRI and gross pathological examination. Conclusion This study confirms the feasibility of a MRI based cryo-ablation system in performing cardiac ablation procedures. The system allows real-time catheter navigation, confirmation of catheter tip–tissue contact, validation of vessel occlusion by cryo-balloon, real-time monitoring of a freeze zone formation, and intra-procedural assessment of ablations including collateral damage.

Characterization of Gadolinium Contrast Enhancement of Radiofrequency Ablation Lesions in Predicting Edema and Chronic Lesion Size

“…5, 6 There is a growing effort to develop real time electrophysiological systems to both create ablation lesions and verify the tissue changes in real time. 16 Here, for the first time we show that LGE-MRI done acutely after ablation can quantify edema in the tissue and correlate the acute MRI findings with chronic lesion formation.…”

Acute noncontrast T1‐weighted magnetic resonance imaging predicts chronic radiofrequency ablation lesions

“…A potential application of MRI is to guide the ablation procedure in real time, which has the promise to provide acute feedback needed for successful lesion delivery . To be effective, the acute MRI methods must also predict reliably the size of the resulting chronic lesions .…”

“…[6][7][8] A potential application of MRI is to guide the ablation procedure in real time, which has the promise to provide acute feedback needed for successful lesion delivery. 9,10 To be effective, the acute MRI methods must also predict reliably the size of the resulting chronic lesions. 11 LGE-MRI can partially provide such information, but due to severe restrictions on contrast administration, this contrast-enhanced imaging technique has been used only at the end of the procedure.…”

Higher contact force during radiofrequency ablation leads to a much larger increase in edema as compared to chronic lesion size

“…It is appealing to envison imaging approaches that could help determine extent of lesion during the procedure. Real‐time MRI techniques provide an immediate and direct means of measuring ablation‐related tissue changes in addition to improved visualization of the tissue, as shown by numerous prior studies . Despite this appeal of using MRI in real time, the techniques are still being developed and are not ready for clinical use .…”

“…Real-time MRI techniques provide an immediate and direct means of measuring ablation-related tissue changes in addition to improved visualization of the tissue, as shown by numerous prior studies. 8,[19][20][21] Despite this appeal of using MRI in real time, the techniques are still being developed and are not ready for clinical use. 22 As a result, one has to rely on indirect mea-surements and test for electrical isolation using functional assays.…”