Abstract 12126: Myocardial Extracellular Volume Imaging by MRI Quantitatively Characterizes Myocardial Infarction and Subclinical Myocardial Fibrosis
Background: Imaging of fibrosis by cardiovascular magnetic resonance (CMR) is routinely performed using late gadolinium enhancement (LGE). However, LGE imaging only visualizes relative differences between “normal” myocardium and fibrosis or infarction. Recent developments in rapid T1 mapping by CMR have made it practical to quantitatively image the extracellular volume fraction (ECV).
Objectives: The aim was to quantify ECV in patients. We hypothesized 1) that ECV imaging could quantitatively differentiate infarction from normal myocardium, 2) that ECV of non-infarcted myocardium would vary with age, and 3) that ECV would vary in myocardium remote from MI.
Methods: Patients (n=96) were imaged at 1.5T (Siemens) with a Modified Look-Locker Inversion-recovery (MOLLI) sequence acquired before and at approximately 15 minutes after a 0.15 mmol/kg bolus of Gd-DTPA. T1 and R1 pixel maps were generated. DeltaR1 maps (R1after - R1before contrast) were divided by the DeltaR1 value of the LV blood pool and multiplied by [1- hematocrit], thus yielding a quantitative pixel map of the ECV fraction ranging from 0–100%. LGE images were acquired for the entire left ventricle.
Results: In patients with no clinically detected focal abnormalities by LGE (n=60, 31 male, mean±SD age 50±17, range 20–79 years), the ECV of the myocardium was (mean±SD) 26±3%. In patients with infarction by LGE (n=36, 31 male, age 58±12, range 37–81), the ECV of remote myocardium was 27±3% (p=ns vs patients with normal LGE) and the ECV of infarcted myocardium was 51±8% (p<0.001). In patients with infarction, the ECV of remote myocardium increased as left ventricular ejection fraction decreased (r=-0.49, p=0.002). In all patients (n=96), as well as both subsets, the ECV of “normal” myocardium increased with age (r=0.27, p=0.004).
Conclusions: ECV imaging is a novel tool for quantitative characterization of both focal and diffuse abnormalities in the myocardium, beyond what is assessable by LGE. Infarctions varied considerably in ECV, but displayed no overlap with ECV of “normal” myocardium. ECV in “normal” myocardium is consistent with age related subclinical fibrosis. ECV also detects a subtle abnormality in myocardium remote from MI which may represent adverse post-infarct remodeling.
- © 2010 by American Heart Association, Inc.