If wall thickening at rest is normal, then – by definition – perfusion must also be normal. However, at peak stress, tissue hypoperfusion may occur in insufficient degrees to reduce contractile function (so wall thickening remains normal) but there is still ischaemia at the tissue level. Thus the sensitivity of MCE is superior to that of DSE (with DSE having superior specificity).
Tsutsui et al published in 2005 a retrospective analysis of 788 patients who had undergone dobutamine stress echocardiography combined with myocardial perfusion assessment (MCE) [67]. A multivariate Cox regression model demonstrated that patients with normal perfusion and normal wall motion had a better prognosis (3yr event-free survival 95%) than those with normal wall motion but abnormal perfusion (3yr event-free survival 82%), underlining the utility of combining MCE in stress echocardiography.
MCE has also been used successfully to assess patients presenting with suspected or confirmed acute coronary syndrome (ACS). MCE is the only technique that allows simultaneous assessment of wall motion and perfusion at the bedside (some ACS patients are too unwell to attend the echo lab). A study of over 1000 patients presenting to the emergency department (ED) with chest pain and negative 12hour troponin underwent rest MCE – the results were more powerful a predictor of outcome than clinical variables, ECG changes and cardiac enzymes [68]. Patients with normal function and perfusion at rest have a good outcome and a negative stress MCE also predicts an excellent prognosis [69].
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