Characterizing extravascular lung water-A dual-contrast agent extracellular volume approach by cardiovascular magnetic resonance.

backgroundPathological extravascular lung water is a facet of decompensated congestive heart failure that current cardiovascular magnetic resonance (CMR) methods fail to quantify. CMR can measure total lung water density, but cannot distinguish between intravascular and extravascular fluid, and thus is not diagnostic. Therefore, we develop and evaluate a novel method to measure extravascular lung water by distinguishing intravascular from extracellular fluid compartments using two different contrast agents, extracellular gadolinium chelates and iron-based intravascular ferumoxytol.

methodsWe created two porcine models of pulmonary edema: reversible catheter-induced mitral regurgitation to induce extravascular lung water (n = 5); intravascular volume overload using rapid colloid infusion (n = 5); and compared to normal controls (n = 8). We sequentially acquired lung T1 maps and lung water density maps at 0.55T with native, gadolinium-based, and ferumoxytol contrast, from which we calculated the extracellular volume fraction (ECV) and blood plasma volume fraction in the pulmonary tissue, respectively. We computed extravascular ECV as the difference in ECV and plasma volume fractions. Extravascular lung water volumes were estimated.

resultsIn the mitral regurgitation model, baseline vs mitral regurgitation ECV

conclusionExtravascular lung ECV measurements and derived lung water volumes corresponded well with predicted increases in extravascular and intravascular pulmonary fluid in animal models. This method may enable mechanistic studies of lung water in patients with dyspnea.