Evaluation of Diffuse Myocardial Fibrosis in Heart Failure With Cardiac Magnetic Resonance Contrast-Enhanced T1 Mapping

ObjectivesThe purpose of this study was to investigate a noninvasive method for quantifying diffuse myocardial fibrosis with cardiac magnetic resonance imaging (CMRI).BackgroundDiffuse myocardial fibrosis is a fundamental process in pathologic remodeling in cardiomyopathy and is postulated to cause increased cardiac stiffness and poor clinical outcomes. Although regional fibrosis is easily imaged with cardiac magnetic resonance, there is currently no noninvasive method for quantifying diffuse myocardial fibrosis.MethodsWe performed CMRI on 45 subjects (25 patients with heart failure, 20 control patients), on a clinical 1.5-T CMRI scanner. A prototype T1 mapping sequence was used to calculate the post-contrast myocardial T1 time as an index of diffuse fibrosis; regional fibrosis was identified by delayed contrast enhancement. Regional and global systolic function was assessed by cine CMRI in standard short- and long-axis planes, with echocardiography used to evaluate diastology. An additional 9 subjects underwent CMRI and endomyocardial biopsy for histologic correlation.ResultsPost-contrast myocardial T1 times correlated histologically with fibrosis (R = −0.7, p = 0.03) and were shorter in heart failure subjects than controls (383 ± 17 ms vs. 564 ± 23 ms, p < 0.0001). The T1 time of heart failure myocardium was shorter than that in controls even when excluding areas of regional fibrosis (429 ± 22 ms vs. 564 ± 23 ms, p < 0.0001). The post-contrast myocardial T1 time shortened as diastolic function worsened (562 ± 24 ms in normal diastolic function vs. 423 ± 33 ms in impaired diastolic function vs. 368 ± 20 ms in restrictive function, p < 0.001).ConclusionsContrast-enhanced CMRI T1 mapping identifies changes in myocardial T1 times in heart failure, which appear to reflect diffuse fibrosis