Patient selection and definition of transcatheter prosthesis size using magnetic resonance imaging: initial experience

Abstract

Introduction: Transcatheter aortic valve replacement requires accurate analysis of aortic annulus, ascending aorta as well as the relation between the aortic annulus and origin of the coronary arteries for correct patient and prosthesis size selection. Multislice computed tomography (MSCT) is currently the preferred imaging modality for preprocedural planning. However, MSCT is associated with radiation exposure and the need for contrast administration. Purpose: This study evaluated whether patient selection and definition of transcatheter prosthesis size can also be derived using cardiac magnetic resonance (CMR). Methods:13 patients (age 79 ± 7) with severe aortic stenosis evaluated for transcatheter aortic valve replacement (Corevalve®) underwent dual-source MSCT (Definition, Siemens, Forchheim, Germany) and CMR (1.5 Tesla, Achieva, Philips, Best, the Netherlands) to define aortic annulus, bulbus and ascending aorta dimensions as well as the distance from the aortic annulus to the left coronary artery. For CMR noncontrast-enhanced navigator-gated 3-D whole heart acquisition was conducted (voxel size 1.2 × 1.2 × 1.8, TR/TE 4.9/2.9, flip angle 100°). CMR-images were analyzed using a 3D-reconstruction tool (EWS, Philips, the Netherlands). Coronal CT-images were reconstructed for evaluation at an external workstation. Results: The aortic annulus diameter was 24 ± 2 mm by MSCT and 24 ± 2 mm by CMR (limits of agreement 3%, r = 0.7, p < 0.001). The diameter of the ascending aorta was 32 ± 4 mm by MSCT and 30 ± 3 mm by CMR (limits of agreement 6%, r = 0.7, p < 0.01). The aortic bulbus diameter was 33 ± 2 mm with MSCT and 30 ± 3 mm measured by CMR (limits of agreement ± 6%, r = 0.4, p = 0.29). The distance of the aortic annulus to the left coronary artery was 14 ± 2 mm by MSCT and 14 ± 2 mm by CMR (limits of agreement 2.2%, r = 0.84, p < 0.01). Based on MSCT measurements, all patients were accepted for aortic revalving. 11 patients (80%) were selected to receive a 26 mm Corevalve® prothesis and 2 patients (15%) were selected to receive a 29 mm prothesis. Based on CMR-measurements the same decision was made in all cases (100%). Conclusion: CMR allows accurate analysis of aortic annulus and ascending aorta dimensions without the need for radiation or contrast-agent exposure. It is non-inferior to MSCT for patient selection and definition of transcatheter prosthesis size. The slight differences between these two methods may be explained by the inferiority of CMR to visualize calcification.