Nonenhanced magnetic resonance imaging for characterization of acute and subacute radiofrequency ablation lesions

w s d i a o s t h t m p The utilization of computed tomography (CT) and magetic resonance imaging (MRI) in the electrophysiology aboratory is increasing steadily. Current clinical use of hese images consists of preprocedural planning of catheter blation procedures for treatment of ventricular tachycardia nd atrial fibrillation utilizing three-dimensional reconstrucions to provide the geometry and sizes of cardiac structures. he reconstructions are integrated with electroanatomic sysems to provide anatomically accurate road maps to guide atheter manipulation. A future phase may use postproceural CT or MRI to assess the long-term success of an blation procedure through quantification of the size and ocation of the ablation lesions and possibly through quanification of changes in cardiovascular function resulting rom the procedure. A yet longer-term phase may involve sing MRI or CT imaging during the ablation process, roviding feedback to the clinician on the locations and uality of the lesions created in real time. The study by ickfeld et al in the current issue of Heart Rhythm is ntended to enable the utilization of MRI for follow-up. The tudy also provides valuable data that would be necessary or proper utilization of intraprocedural MRI. Characterizing radiofrequency (RF) lesions with nonconrast-enhanced MRI is an important goal. Use of gadolinium Gd)-DTPA contrast-enhanced MRI, despite its higher inerent contrast-to-noise ratio, is less desirable for a number f reasons. First, the use of contrast does not allow repeated racking of lesion growth during the delivery of RF current ecause an extended period ( 40–60 minutes) is required etween contrast administrations to allow for kidney clearnce. Second, differentiation of acute from chronic lesions e.g., fibrosis) is difficult with most contrast-enhanced MRI echniques. Third, there are limits to contrast dosages. Fially, there is concern about the possible consequences of d-DTPA not being cleared for lengthy periods from poorly erfused lesion regions, which may lead to ionic Gd, which s toxic, remaining within the body.