Myocardial contrast echocardiography: relation of collateral perfusion to extent of injury and severity of contractile dysfunction in a canine model of coronary thrombosis and reperfusion.

OBJECTIVES: This study sought to determine whether myocardial contrast echocardiography could be used to detect and quantitate collateral blood flow capable of limiting the effects of ischemia in an experimental model of coronary thrombosis and reperfusion. BACKGROUND: Myocardial contrast echocardiography has been used to assess collateral blood flow in humans, but this technique has not been extensively validated in the experimental laboratory. METHODS: Myocardial ischemia occurred after electrically induced left circumflex coronary artery thrombosis in a canine model. Ischemia was intensified by administration of vasodilators. Reperfusion was induced with recombinant tissue-type plasminogen activator. Myocardial perfusion was assessed with contrast echocardiography and radiolabeled microspheres. Infarct size was determined by histochemical staining methods. Myocardial samples were evaluated histologically. RESULTS: The dogs were classified into two groups on the basis of contrast echocardiographic detection of perfusion in the ischemic region: those with (n = 13) and without collateral flow (n = 10). Collateral perfusion detected by contrast echocardiography paralleled changes detected by radiolabeled microspheres during thrombosis and vasodilator administration. A 91% agreement was observed between the two techniques in detecting collateral flow > 0.3 ml/min per g (p < 0.0001). Collateral perfusion correlated directly with radial shortening fractions of the ischemic myocardium (p < 0.01). Recovery of function after reperfusion was faster, infarct size was smaller (mean [+/- SD] 4 +/- 1% vs. 11 +/- 3%, p = 0.05), and histopathologic injury was less in dogs with than without collateral flow, respectively (p < 0.05). CONCLUSIONS: Myocardial contrast echocardiography can identify physiologically significant collateral vessels capable of limiting the degree of ischemic damage during coronary thrombosis. The magnitude of collateral flow and the change in flow induced by vasodilators can be assessed and compares favorably with the microsphere standard.

Myocardial contrast echocardiography: relation between on-line and off-line assessment of myocardial perfusion.

BACKGROUND: Quantitative assessment of myocardial perfusion by myocardial contrast echocardiography has been made possible by the use of custom-made off-line video-intensity programs. A standardized program that could be used by all investigators would improve the reproducibility of results and enhance its clinical utility. METHODS AND RESULTS: The purpose of this study was to determine if the assessment of myocardial perfusion by contrast echocardiography using a new commercially available, quantitative on-line software program correlates with an off-line custom-made video-intensity program previously validated by our laboratory and with radiolabeled microspheres, under various experimental myocardial perfusion conditions. Two of the measured myocardial contrast echocardiographic parameters (peak intensity, area under the time-intensity curve {area}) correlated well among on-line and off-line methods and radiolabeled microspheres, especially when the data were "normalized" by comparing percent change from baseline or a ratio of ischemic to nonischemic myocardium. The third myocardial contrast echocardiographic parameter examined, half-time of the peak intensity on the washout limb of the curve (t 1/2), correlated only when the percent change from baseline was compared between the two methods or when the off-line method was compared with radiolabeled microspheres. CONCLUSION: The results of this investigation add further support to the potential use of myocardial contrast echocardiography to evaluate serial changes in myocardial perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)