T1 mapping in dilated cardiomyopathy with cardiac magnetic resonance: quantification of diffuse myocardial fibrosis and comparison with endomyocardial biopsy.

Abstract

The aim of this study was to determine the value of extracellular volume fraction (ECV) for the non-invasive assessment of diffuse myocardial fibrosis (MF) in different stages of systolic left ventricular (LV) dysfunction in dilated cardiomyopathy (DCM) in comparison with endomyocardial biopsy. Non-invasive ECV assessment using cardiovascular magnetic resonance (CMR) T1 mapping reflects diffuse MF in patients with severe DCM, but earlier stages of DCM with mild LV functional impairment have not been investigated yet. Forty-five subjects with mild functional impairment and LV dilation ['early DCM', ejection fraction (EF) 45-55%], 29 with LV dysfunction and volume dilatation ('DCM', EF <45%) and 56 healthy volunteers (controls) underwent standard CMR imaging, late gadolinium enhancement (LGE) and T1 mapping for the calculation of ECV. The collagen volume fraction (CVF) was quantified histologically from endomyocardial biopsies of 24 DCM patients out of the study cohort. The ECV between 'early DCM' (25 ± 4%), 'DCM' (27 ± 4%), and controls (23 ± 3; P < 0.05 for all) differed significantly. There was a weak inverse correlation between ECV and EF (r = -0.35; P < 0.01). A strong correlation between ECV and CVF could be detected (r = 0.85; P = 0.01). The cut-off value for ECV to differentiate between healthy myocardium and DCM was 26% (specificity 91.1%, sensitivity 62.1%, area under the curve 0.8, P < 0.0001). ECV is already elevated at early stages of functional impairment, whereby an overlap between early DCM and controls is present. But 31% of the early DCM patients had an ECV fraction above the mean ±2 SD ECV of controls. ECV measurement with CMR reflects myocardial collagen content in DCM. Therefore, CMR-based assessment of ECV may have the potential to serve as a non-invasive tool for the quantification of diffuse MF in order to monitor therapy response and aid risk stratification in different stages of DCM.