Extracellular volume imaging by magnetic resonance imaging provides insights into overt and sub-clinical myocardial pathology.

AIMS: Conventional late gadolinium enhancement (LGE) cardiac magnetic resonance can detect myocardial infarction and some forms of non-ischaemic myocardial fibrosis. However, quantitative imaging of extracellular volume fraction (ECV) may be able to detect subtle abnormalities such as diffuse fibrosis or post-infarct remodelling of remote myocardium. The aims were (1) to measure ECV in myocardial infarction and non-ischaemic myocardial fibrosis, (2) to determine whether ECV varies with age, and (3) to detect sub-clinical abnormalities in 'normal appearing' myocardium remote from regions of infarction. METHODS AND
RESULTS: Cardiac magnetic resonance ECV imaging was performed in 126 patients with T1 mapping before and after injection of gadolinium contrast. Conventional LGE images were acquired for the left ventricle. In patients with a prior myocardial infarction, the infarct region had an ECV of 51 ± 8% which did not overlap with the remote 'normal appearing' myocardium that had an ECV of 27 ± 3% (P < 0.001, n = 36). In patients with non-ischaemic cardiomyopathy, the ECV of atypical LGE was 37 ± 6%, whereas the 'normal appearing' myocardium had an ECV of 26 ± 3% (P < 0.001, n = 30). The ECV of 'normal appearing' myocardium increased with age (r = 0.28, P = 0.01, n = 60). The ECV of 'normal appearing' myocardium remote from myocardial infarctions increased as left ventricular ejection fraction decreased (r = -0.50, P = 0.02).
CONCLUSION: Extracellular volume fraction imaging can quantitatively characterize myocardial infarction, atypical diffuse fibrosis, and subtle myocardial abnormalities not clinically apparent on LGE images. Taken within the context of prior literature, these subtle ECV abnormalities are consistent with diffuse fibrosis related to age and changes remote from infarction.