Myocardial scar in aortic stenosis by CMR without contrast

Aortic valve stenosis (AS) is a narrowing of the valve through which the heart pumps blood into the systemic circulation. The presence of a narrowing of this valve places an enormous strain on the left heart, which has to perform significant extra work. As a result of this extra- natural strain, pathological changes occur in the heart muscle if AS persists. These include, among other things, connective tissue accumulations between the heart muscle cells, which can worsen the pumping power of the heart. These connective tissue collections can be visualized on the one hand by analysis of an obtained myocardial sample (=invasively) and on the other hand non-invasively by cardiac magnetic resonance imaging (MRI). In order to be able to characterize cardiac tissue, contrast medium is usually used in cardiac MRI. This contrast agent is generally relatively safe, but can still cause some side effects or cannot be used in some cases (e.g., severe kidney disease). For this reason, there is a need for non- contrast agent examination techniques that can detect/describe the tissue changes described above similarly well. Two of these new contrast agent-free techniques are named T1 and TRAFF. Although still poorly studied, they have great potential as contrast-free alternatives. The current study will now investigate T1 and TRAFF in patients with severe AS undergoing aortic valve replacement surgery. All subjects will undergo simultaneous conventional MRI examinations with the use of contrast and will also have a tissue sample taken during cardiac surgery. This will allow direct comparison of the novel techniques with known analysis methods. The current study is being conducted at Barts Heart Center / University College London in the world-renowned MRI laboratory of Prof. James Moon. The planned duration of the project is 14 months.

It was the aim of the current research to investigate the potential of novel non-contrast cardiac magnetic resonance (CMR) sequences (T1 and TRAFF2 mapping) for the detection of myocardial scar in patients with severe aortic stenosis undergoing surgical aortic valve replacement. To test this hypothesis quantitative mapping results of T1 and TRAFF2 were to be a) compared between AS patients and healthy controls, b) compared to conventional CMR fibrosis markers (T1, ECV), and c) correlated to fibrosis assessed by histological analysis. Due to technical difficulties encountered, TRAFF2 had to be omitted from our research protocols. As expected, patients with AS had higher left ventricular mass, borderline larger left ventricular size, higher right ventricular size, and larger left atria. Native T1 values were numerically higher in AS versus controls. Conversely, no difference between groups was found with regard to T1 values. The lack of significant differences in T1 values between healthy subjects and AS may be explained by the only modest degree of scar/fibrosis in AS compared to other diseases (like amyloid or extensive myocardial infarction). However, simultaneous intra-operative myocardial tissue sampling offered the unique opportunity of correlation with fibrosis on histology - results that are still pending for the current project. This will be the first correlation of T1 and myocardial histology in humans.