Aortic valve stenosis: CT contributions to diagnosis and therapy

As populations in Western civilizations are aging, the prevalence of degenerative aortic valve stenosis is increasing. CT imaging provides information on aortic valve pathology in many ways: In nonenhanced scans, aortic valve calcification can be quantified accurately, which helps to understand the pathogenesis and progression of aortic sclerosis and stenosis. After contrast injection, CT allows excellent visualization of aortic valve structure and, through measurement of the aortic valve area, is capable to serve as a "backup method" for the assessment of aortic valve stenosis, especially if other imaging methods are difficult to interpret. Importantly, CT tends to overestimate aortic valve opening areas in comparison to transthoracic echocardiography, which relies on the continuity equation for quantifying aortic stenosis, based on flow velocities and the estimated area of the left ventricular outflow tract. It has recently been shown that the oval rather than round shape of the left ventricular outflow tract is the most likely factor behind this systematic difference between functional compared with anatomic assessment of aortic valve stenosis. In fact, the ability to provide superbly accurate anatomic imaging of the aortic valve and entire aortic root makes CT a uniquely useful tool for the planning of transcatheter aortic valve implantation. Hence, CT imaging spans a wide range of applications in aortic valve disease, from basic research to diagnosis and treatment planning. This review aims to summarize the current state of the art concerning imaging of the aortic valve by CT and the potential clinical applications.