[Determining myocardial perfusion--contribution of contrast echocardiography]

There is great demand for a non-radioactive bed-side method for the assessment of myocardial perfusion by contrast echocardiography, which may gain clinical relevance for diagnostic strategies only with i.v. application of the contrast agent as opposed to the intracoronary application used until recently. This has finally become true after many years of developing left heart contrast agents and more adequate ultrasound acquisition methods. This leads to the question: Where are we now? Myocardial contrast echocardiography yields unique information on the pathophysiology of microcirculation in vivo due to the fact that microbubbles remain strictly intravascular. Experimental and clinical studies using intracoronary contrast application have shown that infarct size and area at risk are depicted with high accuracy and furthermore that reflow vs no reflow phenomena are demonstrated after the revascularization procedure. In addition, presence and prognostic implications of collateralization may be assessed. Microvascular integrity plays an important role for functional recovery after revascularization. The breakthrough to a potentially clinical role of contrast echocardiography is mainly due to the development of new acquisition methods, such as pulse inversion technique, which allow differentiation of the microbubble signature from the surrounding myocardium. Initial publications show good diagnostic accuracy for the assessment of infarct size and area at risk as well as for the reflow vs no reflow phenomena and microvascular integrity, in particular also as follow up after protective interventions to improve microcirculation. Now, it is conceivable to assess relative or absolute changes of myocardial perfusion. This may be achieved by using non-video signals for analysis and by understanding attenuation effects and other artifacts. Further intensive and critical evaluation and standardization of imaging and analysis techniques is required before general clinical acceptance. New insight into the dynamic nature of perfusion, however, may already allow progress in some urgent questions of microvascular protection.