Extracellular volume imaging by MRI provides insight into overt and subclinical myocardial pathology

Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, US Department of Health and Human Services, 10 Center Drive, Bethesda, MD 20892-1061, USA.
European Heart Journal (Impact Factor: 15.2). 01/2012; 33(10):1268-78. DOI: 10.1093/eurheartj/ehr481
Source: PubMed


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.
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).
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.

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Available from: Martin Ugander
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    • "Edema has been little studied to date. ECV imaging can quantitatively characterize infarcted scar and atypical fibrosis, diffuse myocardial abnormalities — even when not clinically apparent on LGE images — and also the small changes occurring in myocardium with aging, even if near to detection limit [35••, 36]. "
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    ABSTRACT: Heart failure (HF) is a major and growing cause of morbidity and mortality. Despite initial successes, there have been few recent therapeutic advances. A better understanding of HF pathophysiology is needed with renewed focus on the myocardium itself. A new imaging technique is now available that holds promise. T1 mapping is a cardiovascular magnetic resonance (CMR) technique for non-invasive myocardial tissue characterization. T1 alters with disease. Pre-contrast (native) T1 changes with a number of processes such as fibrosis, edema and infiltrations. If a post contrast scan is also done, the extracellular volume fraction (ECV) can be measured, a direct measure of the interstitium and its reciprocal, the cell volume. This dichotomy is fundamental - and now measurable promising more targeted therapy and new insights into disease biology.
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    • "Already, several centers have begun exploring the role of ECV as a novel imaging biomarker of diffuse myocardial fibrosis among those with HCM. From a diagnostic standpoint, Ugander et al [39], Sado et al [40], and Kellman et al [41], all demonstrated the ability of abnormally elevated ECV measurement to discriminate between myocardial regions (and individuals) of health vs disease. Our group has observed a preliminary association between ECV and BNP [42], of interest given the recent observation that BNP may be a relevant HCM disease severity marker [43]. "
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    • "The major outcome of this CMR study using T1 mapping was that in hypertrophic cardiomyopathy areas without late gadolinium enhancement showed a similar extracellular volume fraction (ECV) compared to controls. This is in line with a study by Ugander et al. [17], who reported non-elevated ECV in ‘normal appearing’ myocardium in non-ischemic cardiomyopathies. Study results are not directly comparable however, since the patient population in present study was defined more precisely (HCM only) and thresholding was used to select ROI’s in LGE positive HCM patients instead of visual interpretation. "
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