Real-time perfusion imaging: a new echocardiographic technique for simultaneous evaluation of myocardial perfusion and contraction

Myocardial contrast echocardiography (MCE) with high acoustic energy and triggered harmonic imaging is the best established ultrasound technique to date for the assessment of myocardial perfusion. With this technique, however, the ultimate goal of MCE (noninvasive real-time simultaneous assessment of myocardial perfusion and function after an intravenous injection of microbubbles) is not met. Recently, technologic advances have enabled myocardial opacification to be visualized during low-energy real-time imaging. During real-time perfusion imaging, wall motion and myocardial perfusion may be assessed simultaneously, obviating the need of the presently time-consuming combination of different imaging modalities. When high-energy ultrasound bursts are periodically transmitted to produce bubble destruction during low-power imaging, the consecutive frames after destruction delineate the restoration of contrast intensity. Microbubble replenishment rate and peak intensity may be determined subsequently, and provide reliable quantitative parameters of regional microcirculatory flow. This review will introduce the modalities used for real-time perfusion imaging with focus on power pulse inversion imaging and quantitative analysis. Furthermore, we will describe the clinical role the technique may have in the identification of coronary artery disease, quantification of coronary stenosis severity, assessment of myocardial viability, determination of infarction size, and evaluation of reflow and no- or low-reflow after acute myocardial infarction.