Comparison of Real-Time and Intermittent Triggered Myocardial Contrast Echocardiography for Quantification of Coronary Stenosis Severity and Transmural Perfusion Gradient

Abstract

Background Both intermittent triggered and real-time myocardial contrast echocardiography (MCE) have been proposed to detect impaired myocardial perfusion. We compared the ability of these 2 methods to quantify altered myocardial blood flow (MBF) and transmural distribution of MBF produced by graded coronary stenoses. Methods and Results In 8 open-chest dogs, we created 4 graded left anterior descending coronary artery (LAD) stenoses: 3 levels of reduced adenosine hyperemia (non–flow-limiting at rest) and 1 grade of flow-limiting at rest. Real-time MCE was performed with SonoVue infusion using low-energy power pulse inversion (ATL) imaging, whereas ECG-gated intermittent triggered imaging used high energy at pulsing intervals from 1:1 to 1:10. LAD signal intensity (SI) was plotted versus time by real-time MCE and versus pulsing intervals by triggered MCE and was fitted to a 1-exponential function to obtain plateau SI (A) and the rate of SI rise (b). Visual detection of decreased opacification was equivalent by triggered and real-time MCE. Fluorescent microsphere–derived MBF ratio in LAD/left circumflex artery beds demonstrated close correlation with both real-time imaging (b, r =0.79; A×b, r =0.81) and triggered imaging (b, r =0.78; A×b, r =0.80). The endocardial/epicardial ratio of MBF in the LAD bed demonstrated closer correlation with the endocardial/epicardial ratios of b ( r =0.71) and A×b ( r =0.67) obtained by real-time than triggered imaging (b, r =0.42; A×b, r =0.52). Conclusions Real-time and triggered MCE are equivalent in their ability to identify coronary stenosis and quantify altered MBF.