Role of CT in patients with prosthetic heart valves

Abstract

Valvular heart disease accounts for a substantial part of the cardiovascular disease worldwide with an estimated prevalence of 2.5% in the Western population aged <65 years and over 13% in the population aged >75 years. Surgical prosthetic heart valve (PHV) replacement is the indicated therapy for severe valve disease or in symptomatic patients. PHV-related complications are serious and potentially life threatening and include structural valve deterioration, regurgitation, endocarditis and obstruction. Acquired PHV obstruction is mostly caused by valve thrombosis or pannus (fibrous subprosthetic tissue), whereas valve obstruction presenting early after implantation may be caused by patient prosthesis mismatch. Depending on the cause and severity of dysfunction, the treatment may include antibiotic therapy, anticoagulant therapy, fibrinolysis, redo valve surgery or valve-in-valve implantation and is associated with high morbidity and mortality. Hence, baseline and follow-up imaging after PHV implantation is important to detect and differentiate between these complications and to determine the correct treatment strategy. Transthoracic echocardiography (TTE) is the routine diagnostic imaging modality. In addition, transesohageal echocardiography (TEE) and fluoroscopy may be considered in suspected PHV dysfunction. Although echocardiography is readily available and provides functional information, it may result in an inconclusive diagnostic work-up as it often cannot detect the underlying cause of PHV dysfunction. In this thesis the role of computed tomography (CT) as diagnostic imaging modality in addition to routine work-up in patients with PHVs was evaluated. Presented in vitro results show that compared with fluoroscopy, CT can accurately assess mechanical valve leaflet excursions and detect leaflet restriction. Although the effective radiation dose of retrospectively ECG-gated CT acquisitions may be a drawback, modern iterative reconstruction techniques allow for dose reduction while maintaining good image quality. In patients, CT performed at baseline after PHV implant detected pathology that was not detected with routine TTE imaging including pseudoaneuryms, valve dehiscence and subprosthetic tissue. In suspected PHV dysfunction, additional CT imaging provided complementary information to echocardiography on the underlying cause of PHV dysfunction by detecting subvalvular membrane, pannus and/or thrombus. In mechanical PHVs, CT also resulted in a change of the treatment strategy in a third of patients. In biological valves. CT can be used to detect valve calcifications in (early) structural valve deterioration. In patients with suspected PHV regurgitation, the strength of complementary CT is its ability to detect or exclude infectious complications in both mechanical and biological valves. Furthermore, CT showed relevant for planning redo surgery and percutaneous periprosthetic leak closure as it provides information on PHV-related anatomy, implanted PHV size and can be used for concomitant evaluation of coronary artery stenosis and transcatheter (valve-in-valve) sizing. In conclusion, CT as additional imaging modality has incremental value to echocardiography and fluoroscopy and provides complimentary, readily available information helpful for planning redo surgery or transcatheter procedures. CT should therefore always be considered in all patients with suspected PHV dysfunction and may be considered in selected patients at baseline after PHV implant.