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

Abstract

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 con- trast-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 cardio- vascular 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%) demon- strated 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 ¼ 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, respect- ively (24+ 3 and 24+ 2%, P ¼ 0.005). Global ECV in patients with cardiac involvement substantially correlated to LV ejection fraction (r ¼ 20.629, P ¼ 0.003) and to the number of LGE-positive segments (r ¼ 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 ¼ 0.032). Conclusion ECV measurement by CMR is 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.