Measurement of the gadopentetate dimeglumine partition coefficient in human myocardium in vivo: normal distribution and elevation in acute and chronic infarction.

Abstract

To establish a method for measuring the partition coefficient (lambda) of gadopentetate dimeglumine in humans in vivo, evaluate the spatial and intersubject variation in the lambda of normal myocardium, and compare these values on a regional basis with lambda values of acute and chronic infarcted myocardium. Twelve healthy subjects and patients with acute (n = 5) or chronic (n = 5) myocardial infarction underwent magnetic resonance imaging at 1.5 T. Look-Locker images were acquired at four short-axis levels to measure myocardial and blood longitudinal relaxation time at baseline and after a 30-40-minute infusion of gadopentetate dimeglumine. lambda was calculated as DeltaR1(M)/DeltaR1(B, )where M = myocardium, and B = blood. The magnitude of the estimated lambda in normal myocardium was uniform over the entire myocardium at 0.56 mL/g +/- 0.10 (SD). The lambda values in patients with acute (0.91 mL/g +/- 0.11, P <.001) or chronic (lambda = 0.78 mL/g +/- 0.09, P <.001) infarction were significantly elevated, as compared with those in healthy subjects. A 20% elevation in lambda, as compared with the mean value of a corresponding normal circumferential segment, allowed identification of chronically (sensitivity, 88%; specificity, 96%) or acutely (sensitivity, 100%; specificity, 98%) infarcted segments. Quantification of the lambda in vivo allows differentiation between normal and acutely or chronically infarcted myocardium, with high sensitivity and specificity.