Background-Cardiac MRI offers 3D real-time imaging with unsurpassed soft tissue contrast without x-ray exposure. To minimize safety concerns and imaging artifacts in MR-guided interventional electrophysiology (EP), we aimed at developing a setup including catheters for ablation therapy based on carbon technology. Methods and Results-The setup, including a steerable carbon catheter, was tested for safety, image distortion, and feasibility of diagnostic EP studies and radiofrequency ablation at

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... 5 T. MRI was performed in 3 different 1.5-T whole-body scanners using various receive coils and pulse sequences. To assess unintentional heating of the catheters by radiofrequency pulses of the MR scanner in vitro, a fluoroptic thermometry system was used to record heating at the catheter tip. Programmed stimulation and ablation therapy was performed in 8 pigs. There was no significant heating of the carbon catheters while using short, repetitive radiofrequency pulses from the MR system. Because there was no image distortion when using the carbon catheters, exact targeting of the lesion sites was possible. Both atrial and ventricular radiofrequency ablation procedures including atrioventricular node modulation were performed successfully in the scanner. Potential complications such as pericardial effusion after intentional perforation of the right ventricular free wall during ablation could be monitored in real time as well. Conclusion-We describe a newly developed EP technology for interventional electrophysiology based on carbon catheters. The feasibility of this approach was demonstrated by safety testing and performing EP studies and ablation therapy with carbon catheters in the MRI environment. (Circ Arrhythmia Electrophysiol. 2009;2:258-267.) Key Words: ablation Ⅲ electrophysiology Ⅲ MRI A lthough interventional therapy of complex arrhythmias is becoming more and more common, these approaches are still accompanied by a substantial risk of procedural complications. 1 Therefore, real-time imaging of the surrounding anatomy, lesion mapping, and early detection of complications seem to be crucial for the further development of these interventional approaches.