Non-Invasive Imaging of the Aortic Root : towards optimal evaluation and sizing of stented (tissue engineered) heart valves

In Part I of this thesis the application of multidetector-row computed tomography (MDCT) (Chapter 2) and magnetic resonance imaging (MRI) (Chapter 3) in the imaging of the aortic root has been investigated. Imaging of the stenotic aortic root by echocardiography, MDCT or MRI is relevant for TAVI. Due to the non-invasiveness of this implantation technique, direct visual assessment by the implanting surgeon is impossible. Therefore other imaging techniques are needed to replace direct visual assessment. The role of imaging in TAVI (before, during and after the implantation procedure) is summarized in Chapter 4. Chapter 5 gives an example of the use of multimodality imaging for the visualization of a papillary fibroelastoma of the mitral valve. In Chapter 6 the dynamic changes of the aortic valve annulus during systole and diastole are described in an observational study. In Chapter 7 a post-processing method for quantification of asymmetric aortic distension using MDCT is described and applied to assess asymmetry in the aortic distension over the cardiac cycle in healthy and diseased subjects. In Chapter 8 we describe the potential role of (three-dimensional) echocardiography and MDCT in the guidance of complex re-operative heart valve surgery. Imaging of TAVI prostheses is disturbed by the metal components of the stent surrounding the biological tissue. For example, the role of echocardiography after TAVI is limited due to artifacts. MDCT protocols for the assessment of TAVI prostheses are compared in-vitro. Static (Chapter 9) and dynamic protocols (Chapter 10) are explored to optimize the imaging of stented heart valve prostheses. For the translation of tissue engineered heart valves from bench to bed, adequate protocols for the preclinical in-vivo testing are needed (Part IV). In Chapter 11 the literature on animal experiments for heart valve prostheses and TE heart valves is reviewed from the perspective of the current guidelines developed to guide the tissue engineering concept towards clinical application. In Chapter 12 the protocol used for in-vivo testing of TE heart valves in sheep is described including in-vivo imaging with echocardiography, MDCT and MRI. The first results are included. Our result of the application of MDCT in-vivo in an animal model following implantation of a TE heart valve, is shown in Chapter 13. Finally, the main findings of the different studies presented in this thesis are discussed in Chapter 14 including further aspects for future studies towards optimal evaluation of stented (TE) heart valves.