THE DETERMINATION OF MYOCARDIAL VIABILITY USING GD-DTPA IN A CANINE MODEL OF ACUTE MYOCARDIAL-ISCHEMIA AND REPERFUSION

The partition coefficient of Gd-DTPA was thought to vary with the amou nt of cellular membrane damage after an acute myocardial infarction, T he relationship between the partition coefficient of Gd-DTPA (lambda) and the uptake of (TI)-T-201 (as a marker of tissue viability) was stu died 2 h to 3 weeks after reperfusion of a 2-h occlusion to the left a nterior descending coronary artery in a canine model. Gd-DTPA was infu sed as a bolus followed by a prolonged constant infusion, and this inf usion protocol was optimized such that the concentration of Gd-DTPA wa s directly related to lambda. After this infusion, MR images of excise d hearts showed regions of increased signal intensity corresponding to increased Gd-DTPA concentration, At all time points, lambda and (TI)- T-201 uptake were strongly negatively correlated indicating that lambd a is an accurate indicator of myocardial viability, Furthermore lambda in the infarcted regions was increased relative to normal regions aft er 2 h of reperfusion and stayed elevated up to 3 weeks, At all time p oints, lambda in the infarcted and normal regions were significantly d ifferent, As well, this data showed a trend that lambda in infarcted r egions decreased monotonically from 1 day to 3 weeks, This trend was c onfirmed with MR imaging by examining the change in signal intensity o f 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 m yocardial damage after an acute myocardial infarction.