Computed Tomography of Prosthetic Heart Valves

Prosthetic heart valve (PHV) dysfunction is an infrequent but potentially life-threatening disease with a heterogeneous clinical presentation. Patients with PHV dysfunction clinically can present with symptoms of congestive heart failure (dyspnea, fatigue, edema), fever, angina pectoris, dizziness during exercise or non-specific complaints (e.g. stroke). Non-invasive imaging plays a key role in the establishment of the diagnosis PHV dysfunction. The primary imaging modality for postoperative assessment of PHV function is the transthoracic echocardiography (TTE). TTE is fast, bedside available, patient friendly and relatively cheap compared to more advanced non-invasive imaging techniques. Besides TTE, transesophageal echocardiography (TEE) and fluoroscopy are available in clinical practice for PHV assessment. These imaging techniques may fail to determine the exact cause of PHV dysfunction. Multidetector-row Computed Tomography (MDCT) is a novel imaging technique to evaluate patients with (suspected) prosthetic heart valve dysfunction. In the in vitro part of this thesis, MDCT imaging is optimized for PHV assessment. Different imaging/acquisition strategies are investigated to develop a low-dose MDCT acquisition protocol for PHV imaging with a good image quality and limited PHV-related artifacts. The application of prospective ECG-triggering and iterative reconstruction are promising for low-dose MDCT imaging of PHVs. Although these low-dose MDCT acquisition protocols have to be validated in patients with PHVs. The in vivo part of this thesis demonstrated that MDCT is a suitable imaging technique to visualize most commonly implanted PHVs except for PHVs that contain a cobalt-chrome alloy in the valve ring. This cobalt-chrome alloy causes severe artifacts which preclude diagnostic assessment of these valves on MDCT images. Besides PHV assessment, coronary artery segments can be assessed in most patients simultaneously. Besides PHV composition, annular movement may influence MDCT image quality of PHVs. End-systolic imaging phases (30-40%) and mid-diastolic imaging phases (75-80%) are the best imaging reconstruction phases for PHV assessment. Other imaging phases (10%-20%-50%-60%) have an inferior image quality and can be preferably imaged with dose modulation or omitted in case of prospectively ECG-triggered acquisition. MDCT is a promising complementary imaging modality to echocardiography and fluoroscopy for the evaluation of patients with (suspected) PHV dysfunction. MDCT has additional diagnostic value especially in patients with suspected aortic PHV obstruction and endocarditis. MDCT may visualize the anatomical substrate that causes the PHV obstruction or endocarditis. Besides additional diagnostic information, MDCT can provide additional information for the surgical planning in patients scheduled for reoperation namely (1) the relation of PHV pathology to relevant surrounding cardiac structures (e.g. coronary arteries), (2) the presence of coronary artery disease in patients with low or intermediate risk of coronary artery disease; and (3) aortic dimensions which can have clinical important implications (e.g. the choice for aortic ascendens replacement). Prospective diagnostic cross-sectional studies are required to determine the additional diagnostic value of MDCT to the clinical routine imaging techniques and its impact on patient management. Non-invasive imaging of prosthetic heart valves is a research field in which new imaging techniques (3D TEE, MDCT and hybrid imaging) can improve diagnostic accuracy in patients with suspected PHV dysfunction in the future