Article

Extracellular volume imaging by magnetic resonance imaging provides insights into overt and sub-clinical 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: 14.72). 01/2012; 33(10):1268-78. DOI: 10.1093/eurheartj/ehr481
Source: PubMed

ABSTRACT 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.

0 Bookmarks
 · 
150 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Both post-contrast myocardial T1 and extracellular volume (ECV) have been reported to be associated with diffuse interstitial fibrosis. Recently, the cardiovascular magnetic resonance (CMR) field is recognizing that post-contrast myocardial T1 is sensitive to several confounders and migrating towards ECV as a measure of collagen volume fraction. Several recent studies using widely available Modified Look-Locker Inversion-recovery (MOLLI) have reported ECV cutoff values to distinguish between normal and diseased myocardium. It is unclear if these cutoff values are translatable to different T1 mapping pulse sequences such as arrhythmia-insensitive-rapid (AIR) cardiac T1 mapping, which was recently developed to rapidly image patients with cardiac rhythm disorders. We sought to evaluate, in well-controlled canine and pig experiments, the relative accuracy and precision, as well as intra- and inter-observer variability in data analysis, of ECV measured with AIR as compared with MOLLI. In 16 dogs, as expected, the mean T1 was significantly different (p < 0.001) between MOLLI (891 ± 373 ms) and AIR (1071 ± 503 ms), but, surprisingly, the mean ECV between MOLLI (21.8 ± 2.1%) and AIR (19.6 ± 2.4%) was also significantly different (p < 0.001). Both intra- and inter-observer agreements in T1 calculations were higher for MOLLI than AIR, but intra- and inter-observer agreements in ECV calculations were similar between MOLLI and AIR. In six pigs, the coefficient of repeatability (CR), as defined by the Bland-Altman analysis, in T1 calculation was considerably lower for MOLLI (32.5 ms) than AIR (82.3 ms), and the CR in ECV calculation was also lower for MOLLI (1.8%) than AIR (4.5%). In conclusion, this study shows that MOLLI and AIR yield significantly different T1 and ECV values in large animals and that MOLLI yields higher precision than AIR. Findings from this study suggest that CMR researchers must consider the specific pulse sequence when translating published ECV cutoff values into their own studies. Copyright © 2014 John Wiley & Sons, Ltd.
    NMR in Biomedicine 11/2014; 27(11):1419-26. · 3.56 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Current Cardiovascular Imaging Reports 09/2014; 7:9287.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Endomyocardial biopsy for histological analysis is an important diag-nostic tool in non-ischaemic cardiomyopathy. However, endomyo-cardial biopsy is invasive and associated with some risk, albeit low. The diagnostic yield is also low, because (1) pathology is often hetero-geneous, (2) current interventional techniques do not permit tar-geted biopsy, and (3) histological analysis can be difficult. For these reasons, endomyocardial biopsy has lost favour among adult cardiol-ogists, except in cardiac transplant, where patients usually undergo serial biopsies to monitor graft health. Understandably, a non-invasive alternative to endomyocardial biopsy would be attractive to clinicians and patients alike. The great advantage of cardiovascular magnetic resonance (CMR) compared with other non-invasive imaging modalities is tissue char-acterization. Patterns of late gadolinium enhancement (LGE) can dif-ferentiate between viable and infarcted myocardium, and between ischaemic and non-ischaemic cardiomyopathy. 1 Even though LGE informs diagnosis and prognosis in ischaemic cardiomyopathy, 2 there is less concrete evidence that LGE is as useful in non-ischaemic cardiomyopathy, which is characterized by diffuse myocardial fibro-sis. This is because LGE interpretation relies on relative difference in signal intensity between 'normal' and 'abnormal' myocardium, although quantification using thresholds based on multiples of signal intensity standard deviation (SD) is possible. T 1 mapping has emerged as the most promising CMR technique for the identification and quantification of diffuse fibrosis. There is a growing body of observational data showing that differences exist in myocardial T 1 values between normal subjects and patients with a wide range of disease processes, including dilated or hypertrophic cardiomyopathy, 3 ischaemia, 4 amyloid, 5 iron overload, 6 Takotsubo cardiomyopathy, 7 and myocarditis. 8 T 1 values also identify subclinical
    European Heart Journal – Cardiovascular Imaging 10/2014; · 2.65 Impact Factor

Full-text (2 Sources)

Download
66 Downloads
Available from
Jun 5, 2014