Aims: Magnetic resonance imaging (MRI) in the context of electrophysiology (EP) studies facilitates visualization of complex three-dimensional anatomy and the underlying arrhythmogenic substrate, real-time passive visualization of catheters, atrial and ventricular function and complications, as well as lesion visualization during the ablation without radiation. In the following we report on our first experience of a real-time MRI-guided EP study demonstrating current possibilities and drawbacks.
Methods and results: Five consecutive patients (one male, four female; mean age 66 ± 11 years) with symptomatic arrhythmias, three patients with highly symptomatic typical atrial flutter, presented to our hospital for isthmus ablation, one patient for an EP study and one for slow pathway ablation in atrioventricular node re-entry tachychardia. The four ablations were performed successfully in a conventional EP laboratory and complete bidirectional isthmus block was confirmed in three patients with atrial flutter. After the procedure in the EP laboratory all five patients were transferred to a 1.5 T whole-body MRI scanner (Intera) for a diagnostic EP procedure. Two MRI compatible steerable diagnostic/ablation catheters (Vision) were inserted via the femoral sheaths and manipulated by an experienced electrophysiologist using a commercially available interactive real-time steady-state free precession sequence (repetition time = 3 ms, echo time = 1 ms, flip angle = 35°, slice thickness = 10 mm, frame rate = 8/s). All catheters could be placed successfully in the right atrium and ventricle, confirmed by intracardiac electrograms, using passive catheter tracking. Furthermore, simple programmed stimulation maneuvers were performed. During and after the procedure, no adverse effects were observed in any patients.
Conclusion: To our knowledge, this is the first series of patients with real-time MRI-guided placement of multiple catheters with subsequent performance of stimulation maneuvers. Besides the mentioned benefits, this technology still encounters several limitations, which have to be solved before application in a routine clinical setting. Challenges arise from delineation of precise surface electrocardiogram recordings in the MRI setting along with intracardiac electrograms, easier handling and visualization of catheters, facilitation of immediate defibrillation in the MRI setting and implementation of an active catheter tracking system.