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Myocardial ultrasonic backscatter for characterization of ischemia and reperfusion: relationship to wall motion
B Barzilai1, Z Vered, G A Mohr
1Department of Medicine, Washington University, St. Louis, Missouri.
Insights
Real-time integrated backscatter imaging detects changes in myocardial acoustic properties during ischemia and reperfusion. This technique differentiates ischemic from normal heart tissue, aiding in diagnosis.
Area of Science:
- Cardiovascular Imaging
- Myocardial Physiology
- Diagnostic Ultrasound
Background:
- Cardiac cycle-dependent variation of integrated backscatter is a known phenomenon in normal myocardium.
- Distinguishing myocardial ischemia and reperfusion using real-time imaging requires further investigation.
Purpose of the Study:
- To determine if real-time integrated backscatter imaging can differentiate myocardial ischemia and reperfusion.
- To assess changes in acoustic properties of the myocardium during these events.
Main Methods:
- Performed 10-minute balloon occlusion of the Left Anterior Descending (LAD) coronary artery in dogs, followed by reperfusion.
- Acquired integrated backscatter images at baseline, during occlusion, and up to 120 minutes post-reperfusion.
- Measured magnitude and delay of cyclic variation in myocardial segments, verified by radiolabeled microspheres.
Main Results:
- Ischemic segments showed decreased magnitude and increased normalized delay of cyclic variation (p <= 0.001).
- Reperfusion normalized the magnitude but only partially restored the delay of cyclic variation.
- Persistent wall motion abnormalities were observed despite normalized acoustic parameters post-reperfusion.
Conclusions:
- Real-time integrated backscatter imaging can detect and differentiate myocardial acoustic property changes associated with ischemia and reperfusion.
- The technique offers a promising method for assessing myocardial viability and injury.
- Discrepancies between acoustic parameters and wall motion suggest complex recovery post-reperfusion.
Abstract:
We have previously shown that cardiac cycle-dependent variation of integrated backscatter occurs in normal myocardium. To determine whether myocardial ischemia and reperfusion can be distinguished by real-time integrated backscatter imaging we performed 10 min balloon occlusion of the Left Anterior Descending (LAD) coronary artery followed by reperfusion in 10 closed-chest anesthetized dogs. Images were obtained at baseline, during occlusion, and up to 120 min after reperfusion. We measured the magnitude and delay of cyclic variation of integrated backscatter in segments with and without asynergy. Radiolabeled microspheres were used to verify both ischemia and reperfusion. Ischemic segments exhibited decreased magnitude and increased normalized delay of cyclic variation of integrated backscatter (from 3.3 +/- 0.3 dB to 1.4 +/- 0.2 dB, mean +/- SE; and from 0.95 +/- 0.03 to 1.67 +/- 0.15, respectively, all p less than or equal to 0.001). Reperfusion promptly restored the magnitude of cyclic variation toward normal. However, the delay of the cyclic variation was restored only partially. Wall motion analysis of the ischemic sites revealed persistent abnormalities throughout the reperfusion interval despite return to normal of the magnitude and delay of cyclic variation. Thus, real-time integrated backscatter imaging permits detection and differentiation of changes in myocardial acoustic properties indicative of ischemia and of subsequent reperfusion.