DISCUSSION
Contrast agents in conjunction with very low MI contrast real-time
imaging increase the accuracy of WM assessment, both through endocardial
border enhancement and by simultaneously providing collateral
information on MP (MP defects always precede WM abnormalities), which in
turns enhances the visual capability to detect a WM abnormality, if
present. This can be particularly helpful in cases of poor acoustic
windows, as well as in cases of difficult evaluation of the anterior
wall and of the apex. In this not-unusual context, MCE could be of great
interest in the routine evaluation of wall motion in pts with chest pain
of uncertain origin.
In fact, the importance and usefulness of MCE for better rest WM
assessment in the evaluation of CP has been only partially demonstrated
in the studies reported above, in terms of risk stratification,
diagnostic and prognostic impact as well as cost-efficiency. Most such
studies were actually performed several years ago, most were
single-centre, most used echocardiography machines not anymore
commercially available (as it is also the case for the contrast media
used) and they used impractical long continuous infusion of contrast.
Furthermore, no study compared the usefulness of an enhanced evaluation
of WM by MCE with the standard evaluation of WM by standard
echocardiography (with no contrast), which is probably the most
compelling practical clinical issue.
This could be of great interest in the context of the ED for the
evaluation of CP of unknown origin, even in the current era of
high-sensitivity troponins.
Indeed, we think that there remain many grey-cases in the daily routine
practice, in which MCE could play a key role in detecting chest pain
subtended by previously unknown CAD. For example, in pts without
significant ECG modifications or in whom high sensitivity troponins show
only borderline increase (still below the upper limit) or have no
clearly significant delta. In such cases the more sensitive evaluation
of WM powered by MCE could add diagnostic information, above all in pts
with severe CAD but apparently normal WM at standard echocardiography.
In conclusion, more and contemporary studies are warranted to confirm
the usefulness of MCE in pts with CP despite the availability of high
sensitivity troponins; as shown in the reported cases, we believe that
MCE, through the detection of otherwise apparently and falsely normal WM
could play an important role in the detection of underlying CAD as a
cause of acute/subacute CP admitted to the ED.