Boukatina, Anna

Background: Myocardial reperfusion following prolonged ischemia may paradoxically cause additional injury, including edema and microvascular damage. These structural alterations augment tissue echogenicity measurable by integrated backscatter (IB). We sought to characterize alterations of myocardial IB in an ischemic and then reperfused region of the rat heart. Methods: Myocardial IB in 12 adult male Sprague-Dawley rats was studied at baseline, 60 minutes after left anterior descending coronary artery occlusion, and chronologically after coronary reopening. Short-axis scans of the mid left ventricle were acquired at a frequency of 8 MHz. Mean±SD values of IB were measured in the region of interest at baseline, ischemia, and reperfusion, and assessed by a paired t-test. Results: See figure and table. IB did not significantly change between baseline and ischemia. However, within 1 minute of reperfusion, IB significantly increased, as compared to both baseline and ischemia, and continued to increase until 10 minutes after reperfusion, when a plateau was reached. Conclusions: Myocardial reperfusion following acute prolonged ischemia in a rat heart significantly augments tissue echogenicity. A continuing increase of IB within minutes of the reperfusion onset and the subsequent plateau of elevated IB values suggest progression and completion, respectively, of reperfusion injury, detectable by a high-frequency transducer.