Use of Cardiac Computerized Tomography to Predict Neo–Left Ventricular Outflow Tract Obstruction Before Transcatheter Mitral Valve Replacement

A lthough the incidence of mitral stenosis has declined precipitously in the Western world due to the reduced incidence of rheumatic heart disease, mitral regurgitation remains one of the most common valvular pathologies. Many patients affected by severe mitral valve disease are elderly with multiple comorbidities and are at high risk for traditional open surgical mitral valve repair or replacement. The emergence of minimally invasive strategies for the treatment of mitral regurgitation, such as placement of a percutaneous edge-to-edge device (MitralClip, Abbott, Santa Clara, CA) to help improve the severity of mitral regurgitation has proven a successful alternative to open surgery in selected patients. This technique, however, is not possible in every patient because of anatomic limitations. Another important patient group that can be high risk for operative intervention includes those with degenerative prosthetic mitral valves or annuloplasty rings. The major cause of bioprosthetic mitral valve dysfunction is cusp calcification causing leaflet thickening and stiffening, which can result in valve stenosis with or without concomitant regurgitation related to leaflet tears. Prosthetic valve dysfunction can also result from extensive tissue overgrowth, thrombus, and the development of a paravalvular leak. The 15-year reintervention rate for bioprosthetic mitral valves is 40%, but the mortality rate for surgical bioprosthetic valve rereplacement ranges from 3% to 23%, which is not appropriate for high-risk patients with multiple comorbidities. The recent success of transcatheter aortic valve replacement has led to interest in extending this technique to the mitral valve. There are several transcatheter mitral valves in early development, and clinically there have been multiple reports describing the transcatheter implantation of replacement valves in the mitral position among patients with severe mitral annular calcification, mitral annular rings, or bioprosthetic mitral valves. The emergence of transcatheter mitral valve replacement (TMVR) as a distinct procedure presents a unique challenge to clinicians. The complex anatomy of the mitral valve annulus and its proximity to the left ventricular outflow tract (LVOT) make preprocedural evaluation crucial. There is an important need to understand the 3-dimensional (3D) relationship between the aortic and mitral valves in order to select an appropriately sized valve and predict whether TMVR will result in obstruction of the left ventricular outflow track from the anterior leaflet of the mitral valve. In this article we provide an overview of how to use cardiac computed tomography (CT) to project neo-LVOT measurements pre-TMVR and illustrate how this technique has performed across a series of clinical cases.