Objectives - This study sought to determine microstructural cardiac remodeling in aortic stenosis (AS) and its reversibility following valve replacement using cardiovascular magnetic resonance (CMR) diffusion tensor imaging (DTI).
Background - Myocardial involvement in AS, such as focal and diffuse fibrosis is associated with worse outcome, even after timely aortic valve replacement (AVR). Alterations of myofiber architecture and myocardial diffusion may precede fibrosis, but its extent and reversibility after AVR are unknown.
Methods - Patients with isolated severe AS (n=21, 62% male; mean age 75 years) and sex-matched senior control subjects underwent prospective CMR DTI. Changes in the DTI parameters: mean diffusivity (MD), fractional anisotropy (FA) as well as helix angle (HA) and absolute E2A sheet angle (E2A) were quantified and compared with native T1 and extracellular volume (ECV) as standard CMR markers of myocardial fibrosis. Six months after AVR eleven patients were scheduled for a follow-up CMR.
Results - In AS patients, significantly elevated MD (p=0.002) and reduced FA (p<0.001) were measured when compared to controls. Myocyte aggregate orientation exhibited a steeper transmural HA slope (p<0.001) and increased absolute E2A sheet angle (p<0.001) in AS. Six months post AVR, the HA slope (p<0.001) was reduced to the level of healthy controls and MD (p=0.014), FA (p=0.011) and E2A (p=0.003) showed a significant regression towards normal values. In contrast, native T1 was similar in AS and controls and did not change significantly after AVR. ECV showed a non-significant trend (p=0.16) to higher values after AVR.
Conclusion - In patients with severe aortic stenosis, CMR DTI provides a set of parameters that identifies structural and diffusion abnormalities, which are largely reversible after AVR. DTI parameters showed proportionally greater changes in response to AS and AVR compared to metrics of myocardial fibrosis and may, therefore, aid risk stratification in earlier stages of severe AS.
Characterization of diffuse fibrosis in the failing human heart via diffusion tensor imaging and quantitative histological validation
