1357377 - Peri-procedural non-gadolinium-based atrial tissue characterization during real-time magnetic resonance guided ablation of right atrial flutter

The present case demonstrates a real-time interventional cardiac magnetic resonance imaging (iCMR)-guided cavotricuspid isthmus (CTI) ablation performed in a 60 years old male patient. The patient had a history of obesity, hypertension, and supraventricular tachycardia (atrial fibrillation but predominantly atrial flutter). To treat his atrial flutter, the patient was referred to our hospital to undergo a flutter ablation. After consultation with the attending physician, the patient expressed a preference for undergoing the flutter ablation in a MRI environment as an alternative to X-ray fluoroscopy without ionizing radiation exposure.

MRI-guided ablation was performed in a conventional 1.5T diagnostic MRI scanner (Avanto, Siemens, Erlangen, Germany) using two first generation MRI-compatible mapping and radio frequency ablation catheters (Imricor, Burnsville, United States). The active catheter imaging method was applied to visualize and navigate the catheters. Two built-in coils in the tip of the catheter connected to the scanner provided a bright signal during imaging. These signals were used to track the position of the catheters during real-time imaging. The mapping catheter was navigated in the coronary sinus. The second catheter was used for targeted ablation of the CTI. Complete isthmus block was achieved after an uncomplicated CTI-ablation. Immediately after ablation, advanced imaging was performed to visualize and characterize the acute ablation lesion.

Diagnostic Techniques and Their Most Important Findings:

T2-weighted images obtained within five minutes after the final ablation showed a substantially increased wall thickness and enhanced signal intensity, indicating extensive edema at the CTI-region. Non-Gadolinium (‘non-contrast’) enhanced T1-weigthed 3D imaging demonstrated a focal enhanced area at the CTI-region. This area was substantially smaller compared to the area with high signal intensity on the T2-weigthed images. Post-ablation 3D late gadolinium enhancement (LGE) images showed also an area with hyperenhancement in the CTI-region. Compared to the non-contrast enhanced T1-weighted images, this area was larger but in comparison to T2-weigthed imaging, this area is smaller.

Learning Points from this Case:

In conclusion, this case demonstrates that iCMR-guided catheter ablation using real-time active catheter imaging is feasible in a diagnostic MRI scanner. Anatomical structures including pouches in the cavotricuspid isthmus could be clearly visualized. Catheters could be easily tracked and navigated by MRI-guidance. Created ablation lesions could be visualized without the need for Gadolinium by applying T1-weigthed 3D imaging. This offers the prospect of peri-procedural feedback during ablation procedures.