Impaired myocardial perfusion in moderate asymptomatic aortic stenosis relates to longitudinal strain but not non-contrast T1 values

Abstract

Background Myocardial perfusion and strain (in particular longitudinal strain- LS) are reduced in severe aortic stenosis (AS). It is thought that reduced perfusion occurs in the subendocardium secondary to increased LV pressure, leading to fibrosis and reduced LS. This relationship between perfusion, diffuse fibrosis and multidirectional myocardial strain has not been previously investigated in moderate (or severe) AS. We hypothesized that impaired myocardial perfusion occurs in patients with moderate AS, leading to a degree of diffuse fibrosis (reflected in increased non-contrast T1 values) and impaired longitudinal strain. Methods 32 patients with moderate AS (by echo criteria) and 12 age and sex-matched normal controls were recruited. All subjects underwent CMR scanning at 1.5T including valve assessment, stress and rest perfusion, tagging, and non-contrast T1-mapping using the ShMOLLI (Shortened Modified Look-Locker Inversion recovery) sequence, which was previously shown to have a good correlation with histological quantification of diffuse fibrosis. Myocardial perfusion reserve index (MPRI) and strain values were derived from analysis of the perfusion and tagging sequences respectively. Results Despite being well matched for age and sex, there were significant differences between patients with moderate AS and normal controls in longitudinal strain, MPRI and LV mass (p<0.0001, Table 1). There were no significant differences in circumferential strain and T1 values between the two groups. In AS patients there was a moderate correlation with MPRI and LS (r = -0.4, p<0.05), but not circumferential strain (CS). In AS patients T1 values correlated