Non-contrast myocardial T1 global and regional reference values at 3 Tesla cardiac magnetic resonance in aortic stenosis

Abstract

T1 mapping using cardiac magnetic resonance (CMR) was recently proposed as a promising non-contrast imaging technique for the assessment of diffuse myocardial fibrosis (MF) in aortic stenosis (AS). To provide reference values for native T1 mapping at 3 Tesla magnetic field strength in subjects with moderate or severe AS and in control subjects; to identify factors associated with the presence of diffuse MF in severe AS; to assess the regional distribution of diffuse MF; and to compare the level of diffuse MF in the different types of AS, stratified by flow and gradient patterns. Retrospective study based on 160 consecutive patients with moderate (n=11) to severe (n=149) AS and 47 control subjects referred for CMR. Mean native T1 increased progressively across controls (1221±23ms), moderate AS (1249±26ms) and severe AS (1273±43ms). T1 times correlated significantly with left ventricular (LV) remodelling (indexed LV mass and LV diastolic volume) and functional LV alterations (global longitudinal strain and LV ejection fraction). Native T1 appears to be elevated in the basal segments of the septum in moderate AS, and to extend to midventricular and apical segments in severe AS. Mean T1 time was higher in classical low-flow/low-gradient AS (1295±62ms) than in the other types of AS (P=0.006). The level of diffuse MF in paradoxical low-flow/low-gradient AS (1280±42ms) was higher than in moderate AS, but similar to that in high-gradient AS (1271±42ms) (P=0.07). Assessment of diffuse MF in AS using T1 mapping is feasible and reproducible in clinical practice. T1 value increases with AS severity, along with morphological and functional LV alterations, particularly in the basal segments of the septum.