Extracellular volume fractions are not consistent in gray zones determined by late gadolinium enhancement imaging of myocardial infarction

Background Patients with prior myocardial infarctions have a large amount injured myocardial tissue which becomes replaced with fibrotic tissue over time. In the periphery of this scar tissue resides tissue that is a mixture of normal myocardium and scar tissue which has anisotropic conduction properties. Late gadolinium enhancement imaging (LGE) has been used to delineate this area known as gray zone. The amount of gray zone has been shown to be associated with the relative arrhythmia risk of patients with prior myocardial infarction. The aim of the study is to determine whether a common gray zone characterization method identifies physiologically equivalent areas across different subjects. The extracellular volume fraction (ECV) is quantitative measurement of fibrosis density calculated using preand post-contrast T1 maps. We hypothesize that ECV measurements in LGE-determined gray zone will show significant inter-subject variability.