Myocardial fibrosis imaging based on T1-mapping and extracellular volume fraction (ECV) measurement in muscular dystrophy patients: diagnostic value compared with conventional late gadolinium enhancement (LGE) imaging

Aim Cardiac involvement with progressive myocardial fibrosis leading to dilated cardiomyopathy is a major cause of death in muscular dystrophy patients. Extracellular volume fraction(ECV) measurement based on T1-mapping pre- and post-contrast promises the detection of early 'diffuse' myocardial fibrosis that cannot be depicted by conventional contrast- imaging based on late gadolinium enhancement (LGE). With this study, we evaluated the presence of diffuse myocardial fibrosis in regions of 'normal' (LGE-negative) and 'diseased' (LGE-positive) appearing myocardium as well as its relation to the extent of left ventricular(LV) dysfunction and the occurrence of arrhythmias in Becker muscular dystrophy(BMD) patients. Methods and results Twenty-seven BMD patients(35 +/- 12 years) and 17 matched male healthy controls(33 +/- 8 years) underwent cardiovascular magnetic resonance(CMR) studies including ECV measurement and LGE-imaging. Ambulatory monitoring of arrhythmic events was performed by means of an external event loop recorder. Twenty BMD patients(74%) demonstrated cardiac involvement as detected by typical inferolateral presence of LGE. Twelve patients(44%) had an impaired LV ejection fraction-all being LGE-positive. Global myocardial ECV was significantly higher in the BMD group(29 +/- 6%) compared with the control group(24 +/- 2%, P = 0.001). Patients with cardiac involvement demonstrated higher global ECV(31 +/- 6%) as well as significantly increased regional ECV not only in LGE-positive segments(34 +/- 6%), but also in LGE-negative segments(28 +/- 6%) compared with BMD patients without cardiac involvement and to controls, respectively (24 +/- 3 and 24 +/- 2%, P = 0.005). Global ECV in patients with cardiac involvement substantially correlated to LV ejection fraction(r = -0.629, P = 0.003) and to the number of LGE-positive segments(r = 0.783, P, 0.001). On univariable analysis, global ECV-but not the categorical presence of LGE per se--was significantly associated with arrhythmic events(OR: 1.97, CI: 32.22-1.21, P = 0.032). Conclusion ECV measurement byCMRis a useful tool in assessing the total extent of myocardial fibrosis as well as in depicting subtle diffuse fibrosis in areas of normal appearing myocardium on LGE-images. Thus, myocardial ECV is a potential additional quantitative tool for accurate detection of cardiac involvement and risk stratification in muscular dystrophy patients.