Cardiac Three-Dimensional Magnetic Resonance Imaging and Fluoroscopy Merging A New Approach for Electroanatomic Mapping to Assist Catheter Ablation

Background—Modern nonfluoroscopic mapping systems construct 3D electroanatomic maps by tracking intracardiac catheters. They require specialized catheters and/or dedicated hardware. We developed a new method for electroana-tomic mapping by merging detailed 3D models of the endocardial cavities with fluoroscopic images without the need for specialized hardware. This developmental work focused on the right atrium because of the difficulties in visualizing its anatomic landmarks in 3D with current approaches. Methods and Results—Cardiac MRI images were acquired in 39 patients referred for radiofrequency catheter ablation using balanced steady state free-precession sequences. We optimized acquisition and developed software for construction of detailed 3D models, after contouring of endocardial cavities with cross-checking of different imaging planes. 3D models were then merged with biplane fluoroscopic images by methods for image calibration and registration implemented in a custom software application. The feasibility and accuracy of this merging process were determined in heart-cast experiments and electroanatomic mapping in patients. Right atrial dimensions and relevant anatomic landmarks could be identified and measured in all 3D models. Cephalocaudal, posteroanterior, and lateroseptal diameters were, respectively, 6511, 5411, and 579 mm; posterior isthmus length was 266 mm; Eustachian valve height was 55 mm; and coronary sinus ostium height and width were 163 and 123 mm, respectively (n39). The average alignment error was 0.20.3 mm in heart casts (n40) and 1.9 to 2.5 mm in patient experiments (n9), ie