Cardiovascular Imaging of Remote Myocardial Ischemia

Intravenous microbubbles currently are approved by the Food and Drug Administration solely for the purpose of enhancing left ventricular cavity opacification. However, intravenous microbubbles also have been used in several clinical studies to detect myocardial perfusion. Ultrasound imaging of myocardial contrast to detect perfusion abnormalities has significant advantages over other imaging techniques in that it has higher resolution, does not require ionizing radiation, and can be performed at the patient’s bedside. Clinical studies have demonstrated that myocardial contrast echocardiography is useful for detecting coronary artery disease both in the emergency room setting and during stress echocardiography. In these settings, the intravenous microbubbles function as pure intravascular tracers and are not adherent to the vessel wall or taken up by the myocytes.Article p 345 Ligands can be attached to the surface of microbubbles, which results in their binding to specific epitopes upregulated on the endothelial surface. Such binding was used in the study by Villanueva et al1 in the present issue of Circulation . In a rat model, these investigators were able to successfully attach the selectin-targeting tetrasaccharide sialyl Lewisx to phospholipid-shelled microbubbles and to detect myocardial regions that were previously ischemic with a sensitive ultrasound detection scheme. Detection of contrast enhancement from retained microbubbles within the remotely ischemic perfusion …