BACKGROUND: Diffuse myocardial fibrosis, and to a lesser extent global 
myocardial edema, are important processes in heart disease which are difficult 
to assess or quantify with cardiovascular magnetic resonance (CMR) using 
conventional late gadolinium enhancement (LGE) or T1-mapping. Measurement of the 
myocardial extracellular volume fraction (ECV) circumvents factors that confound 
T1-weighted images or T1-maps. We hypothesized that quantitative assessment of 
myocardial ECV would be clinically useful for detecting both focal and diffuse 
myocardial abnormalities in a variety of common and uncommon heart diseases.
METHODS: A total of 156 subjects were imaged including 62 with normal findings, 
33 patients with chronic myocardial infarction (MI), 33 with hypertrophic 
cardiomyopathy (HCM), 15 with non-ischemic dilated cardiomyopathy (DCM), 7 with 
acute myocarditis, 4 with cardiac amyloidosis, and 2 with systemic capillary 
leak syndrome (SCLS). Motion corrected ECV maps were generated automatically 
from T1-maps acquired pre- and post-contrast calibrated by blood hematocrit. 
Abnormally-elevated ECV was defined as >2SD from the mean ECV in individuals 
with normal findings. In HCM the size of regions of LGE was quantified as the 
region >2 SD from remote.
RESULTS: Mean ECV of 62 normal individuals was 25.4 ± 2.5% (m ± SD), normal 
range 20.4%-30.4%. Mean ECV within the core of chronic myocardial infarctions 
(without MVO) (N=33) measured 68.5 ± 8.6% (p<0.001 vs normal). In HCM, the 
extent of abnormally elevated ECV correlated to the extent of LGE (r=0.72, 
p<0.001) but had a systematically greater extent by ECV (mean difference 19 ± 7% 
of slice). Abnormally elevated ECV was identified in 4 of 16 patients with 
non-ischemic DCM (38.1 ± 1.9% (p<0.001 vs normal) and LGE in the same slice 
appeared "normal" in 2 of these 4 patients. Mean ECV values in other disease 
entities ranged 32-60% for cardiac amyloidosis (N=4), 40-41% for systemic 
capillary leak syndrome (N=2), and 39-56% within abnormal regions affected by 
myocarditis (N=7).
CONCLUSIONS: ECV mapping appears promising to complement LGE imaging in cases of 
more homogenously diffuse disease. The ability to display ECV maps in units that 
are physiologically intuitive and may be interpreted on an absolute scale offers 
the potential for detection of diffuse disease and measurement of the extent and 
severity of abnormal regions.