Transcatheter Aortic Valve Replacement: Imaging Techniques for Aortic Root Sizing.

Transcatheter aortic valve replacement (TAVR) is an increasingly used alternative to surgical aortic valve replacement in patients with severe aortic stenosis and prohibitive perioperative risk. Several studies have shown an improved clinical outcome and lower rate of complications with TAVR in this patient population. Furthermore, TAVR has shown promising results in patients at elevated risk from surgical aortic valve replacement. Because of the endovascular nature of this technique, comprehensive preprocedural assessment of the aortic root and vascular access path is crucial. Although echocardiography is still commonly performed to assess the aortic root, cross-sectional imaging modalities are increasingly used given their superior results in the diagnostic accuracy of TAVR measurements. In particular, computed tomography (CT) is gaining an increasing role in pre-TAVR imaging because of fast 3-dimensional assessment of aortic root anatomy and improvements in clinical outcome after TAVR when CT is used for pre-TAVR planning. However, different algorithms exist for matching valve size to the aortic root and left ventricular outflow tract, and these measurements may substantially impact valve prosthesis selection and postinterventional complication rates. Cardiac magnetic resonance may play a role especially in post-TAVR assessment, as it provides both anatomic information and blood flow dynamics. This article reviews multimodality imaging approaches to pre-TAVR aortic root size assessment, provides an overview of the impact on post-TAVR complications and clinical outcome, and describes recent techniques to reduce contrast material volume in TAVR assessment with CT.