Assessment of diffuse myocardial fibrosis by using MR imaging in asymptomatic patients with aortic stenosis.

PURPOSE: To assess whether native T1 mapping provides noninvasive estimation of diffuse myocardial fibrosis and whether it correlates with subclinical myocardial dysfunction in asymptomatic patients with aortic stenosis (AS).
MATERIALS AND METHODS: The local institutional review board approved the study, and all patients gave informed consent. Eighty asymptomatic patients with moderate or severe AS and normal left ventricular (LV) ejection fraction (mean age, 67 years; range, 31-81 years) and 15 sex-matched control subjects (mean age, 33 years; range, 23-41 years) were prospectively enrolled. Patients underwent two-dimensional echocardiography, speckle tracking imaging, and cardiac 3.0-T magnetic resonance (MR) imaging, including mapping of T1 relaxation time by using the modified Look-Locker inversion-recovery sequence. Correlations between native T1 values and the degree of diffuse fibrosis in myocardial specimens obtained during aortic valve replacement surgery were analyzed in a subset of 20 patients. Correlations between parameters of myocardial function and structure and native T1 values were assessed with Pearson correlation coefficients.
RESULTS: Native T1 values correlated well with the degree of diffuse myocardial fibrosis in intraoperative myocardial biopsy specimens (r = 0.777, P < .001) and differed significantly between patients with AS and control subjects (1208 msec ± 45 vs 1169 msec ± 21, P < .001). LV volumes and mass differed significantly according to AS groups, categorized by T1 tertiles (all P < .001), as well as degree of AS severity (0.55 cm(2)/m(2) ± 0.14 for lowest native T1 tertile, 0.46 cm(2)/m(2) ± 0.12 for middle native T1 tertile, and 0.45 cm(2)/m(2) ± 0.13 for highest native T1 tertile [P = .008] for indexed aortic valve area at echocardiography). Native T1 correlated significantly with global longitudinal strain measured with two-dimensional speckle tracking imaging (r = 0.598, P < .001), e' velocity (r = -0.437, P < .001), and indexed left atrial volume (r = 0.475, P < .001).
CONCLUSION: Native T1 mapping provides a noninvasive estimation of diffuse myocardial fibrosis and correlates with subclinical myocardial dysfunction in asymptomatic patients with AS. © RSNA, 2014.