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.