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BASIC SCIENCE

Visualization of risk-area myocardium as a high-intensity, hyperenhanced "hot spot" by myocardial contrast echocardiography following coronary reperfusion

Quantitative analysis

^* Division of Cardiology, University of California at San Diego, San Diego, California, USA. Dr. DeMaria has received grants and has been a sponsored speaker or occasional ad hoc consultant both for Bracco Pharmaceuticals, the manufacturer of BR-14, and virtually all other ultrasound contrast manufacturers. A. Jamil Tajik, MD, FACC, acted as the Guest Editor for this paper

Manuscript received October 7, 2002; revised manuscript received April 7, 2003, accepted April 24, 2003.

^* Reprint requests and correspondence: Dr. Anthony N. DeMaria, Division of Cardiology, UCSD Medical Center, 200 West Arbor Drive, San Diego, California 92103-8411, USA.
ademaria{at}ucsd.edu

OBJECTIVES: We examined whether delayed post-injection imaging of a new ultrasound contrast agent (BR-14) could produce prolonged opacification and hyperenhancement of myocardium subjected to coronary occlusion/reperfusion.

BACKGROUND: We hypothesized that ultrasound exposure destroyed BR-14 and eliminated visualization of sustained myocardial opacification from retained microbubbles.

METHODS: We studied eight open-chest dogs with 3 h of left anterior descending coronary artery (LAD) occlusion followed by 3 h of reperfusion. Myocardial contrast echocardiography (MCE) was performed before occlusion and 120 min after the onset of both occlusion and reperfusion. Ultrasound imaging was initiated 15 min after injection. Myocardial blood flow (MBF) was assessed by microspheres.

RESULTS: Pre-occlusion images revealed uniform opacification of left ventricular myocardium greater than that of the cavity, with a mean intensity of the LAD bed of 8.66 ± 1.38 dB. During occlusion, MCE resulted in the appearance of a perfusion defect in the LAD risk area (intensity 2.08 ± 1.10 dB). After 120 min of reperfusion, the LAD risk-area myocardium manifested dense opacification of a higher intensity ("hot spot") than baseline (13.7 vs. 8.7 dB), but with reduced MBF consistent with accumulation of a high concentration of microbubbles. Increased MCE intensity was associated with a greater myeloperoxidase score.

CONCLUSIONS: These data establish that contrast opacification by BR-14 may be selectively retained within the perfusion bed of a coronary artery subjected to occlusion/reperfusion. Such opacification exhibits defects with occlusion, manifests hyperenhanced intensity (hot spot) with reperfusion, is associated with the level of myeloperoxidase activity, and conforms to the area of myocardium subjected to altered flow.

Abbreviations and Acronyms   LAD   left anterior descending coronary artery   LV   left ventricular   MBF   myocardial blood flow   MCE   myocardial contrast echocardiography   TTC   triphenyltetrazolium chloride

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