The determination of myocardial viability using Gd‐DTPA in a canine model of acute myocardial ischemia and reperfusion

Abstract

The partition coefficient of Gd‐DTPA was thought to vary with the amount of cellular membrane damage after an acute myocardial infarction. The relationship between the partition coefficient of Gd‐DTPA (λ) and the uptake of ²⁰¹TI (as a marker of tissue viability) was studied 2 h to 3 weeks after reperfusion of a 2‐h occlusion to the left anterior descending coronary artery in a canine model. Gd‐DTPA was infused as a bolus followed by a prolonged constant infusion, and this infusion protocol was optimized such that the concentration of Gd‐DTPA was directly related to λ. After this infusion, MR images of excised hearts showed regions of increased signal intensity corresponding to increased Gd‐DTPA concentration. At all time points, λ and ²⁰¹TI uptake were strongly negatively correlated indicating that λ is an accurate indicator of myocardial viability. Furthermore, λ in the infarcted regions was increased relative to normal regions after 2 h of reperfusion and stayed elevated up to 3 weeks. At all time points, λ in the infarcted and normal regions were significantly different. As well, this data showed a trend that λ in infarcted regions decreased monotonically from 1 day to 3 weeks. This trend was confirmed with MR imaging by examining the change in signal intensity of in vivo images from 4 days to 3 weeks in two animals. These results suggest that MRI with Gd‐DTPA could be used to measure the extent of myocardial damage after an acute myocardial infarction.