Assessment of myocardial perfusion - role of contrast echocardiography

There is great demand for a non-radioactive bedside method for the assessme nt of myocardial perfusion by contrast echocardiography, which may gain cli nical relevance for diagnostic strategies only with i.v. application of the contrast agent as opposed to the intracoronary application used until rece ntly. This has finally become true after many years of developing left hear t contrast agents and more adequate ultrasound acquisition methods. This le ads to the question: Where are we now? Myocardial contrast echocardiography yields unique information on the patho physiology of microcirculation in vivo due to the fact that microbubbles re main strictly intravascular. Experimental and clinical studies using intrac oronary contrast application have shown that infarct size and area at risk are depicted with high accuracy and furthermore that reflow vs no reflow ph enomena 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 a fter revascularization. The breakthrough to a potentially clinical role of contrast echo cardiograp hy is mainly due to the development of new acquisition methods, such as pul se inversion technique, which allow differentiation of the microbubble sign ature from the surrounding myocardium. Initial publications show good diagn ostic 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 pa rticular also as follow up after protective interventions to improve microc irculation. Now, it is conceiveable to assess relative or absolute changes of myocardial perfusion. This may be achieved by using non-video signals fo r analysis and by understanding attenuation effects and other artifacts. Further intensive and critical evaluation and standardization of imaging an d analysis techniques is required before general clinical acceptance. New i nsight into the dynamic nature of perfusion, however, may already allow pro gress in some urgent questions of microvascular protection.