Histological Validation of measurement of diffuse interstitial myocardial fibrosis by myocardial extravascular volume fraction from Modified Look-Locker imaging (MOLLI) T1 mapping at 3 T

Background: gadolinium (gd) extracellular volume fraction (ecv) by cardiovascular magnetic resonance (cmr) has been proposed as a non-invasive method for assessment of diffuse myocardial fibrosis. yet only few studies used 3 t cmr to measure ecv,and the accuracy of ecv measurements at 3 t has not been established. therefore the aims of the present study were to validate measurement of ecv by molli t1 mapping by 3 t cmr against fibrosis measured by histopathology. we also evaluated the recently proposed hypothesis that native-t1 mapping without contrast injection would be sufficient to detect fibrosis. methods: 31 patients (age∈=∈58∈±∈17 years,77 % men) with either severe aortic stenosis (n∈=∈12) severe aortic regurgitation (n∈=∈9) or severe mitral regurgitation (n∈=∈10),all free of coronary artery disease,underwent 3 t-cmr with late gadolinium enhancement (lge) and pre- and post-contrast molli t1 mapping and ecv computation,prior to valve surgery. lv biopsies were performed at the time of surgery,a median 13 [1-30] days later,and stained with picrosirius red. pre-,and post-contrast t1 values,ecv,and amount of lge were compared against magnitude of fibrosis by histopathology by pearson correlation coefficients. results: the average amount of interstitial fibrosis by picrosirius red staining in biopsy samples was 6.1∈±∈4.3 %. ecv computed from pre-post contrast molli t1 time changes was 28.9∈±∈5.5 %,and correlated (r∈=∈0.78,p∈<∈0.001) strongly with the magnitude of histological fibrosis. by opposition,neither amount of lge (r∈=∈0.17,p∈=∈0.36) nor native pre-contrast myocardial t1 time (r∈=∈-0.18,p∈=∈0.32) correlated with fibrosis by histopathology. conclusions: ecv determined by 3 t cmr t1 molli images closely correlates with histologically determined diffuse interstitial fibrosis,providing a non-invasive estimation for quantification of interstitial fibrosis in patients with valve diseases. by opposition,neither non-contrast t1 times nor the amount of lge were indicative of the magnitude of diffuse interstitial fibrosis measured by histopathology. © 2015 de meester de ravenstein et al.; licensee biomed central.