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.