Diagnostic and prognostic use of stress echo in acute coronary syndromes including emergency department imaging.

Early treatment of acute myocardial infarction (AMI) can improve the rate of coronary patency, salvage myocardium, and ultimately save lives; thus, rapid recognition of patients at a higher risk of developing AMI is very important. The clinical history in patients with documented AMI is sometimes atypical, and the initial cardiac enzyme levels often are within the normal range. Moreover, the typical ST-segment elevation is often absent on the initial electrocardiogram in patients who subsequently sustain an AMI. Stress-induced segmental wall motion abnormalities (SWMAs) in coronary artery disease patients can be readily detected by conventional two-dimensional echocardiography. Moreover, echocardiography is the only technique available that allows real-time assessment of stress-induced reduction in systolic wall thickening, a highly specific sign of myocardial ischemia. Echocardiography for the diagnosis of acute ischemia is most helpful in subjects with a high clinical suspicion but nondiagnostic electrocardiograms. Under these circumstances, reversible SWMA confirms the diagnosis of acute coronary syndrome. The location of regional SWMAs correlates well with the distribution of the artery involved and pathological evidence of infarction. A trained eye can easily recognize cardiac causes of acute chest pain other than coronary diseases such as aortic stenosis, hypertrophic cardiomyopathy, mitral valve prolapse, pericarditis, and aortic dissection. When echocardiography is performed soon after the patients arrival at the emergency department (ED) or during a chest pain episode, SWMAs are detected in 90-95% of transmural infarctions and in 80-90% of nontransmural or subendocardial infarctions, and the specificity of echocardiography is approximately 80-90%. Although stress echocardiography performed in the ED and interpreted at a distance through the use of telemedicine has the potential of being convenient, in our opinion, any form of stress echocardiography should be performed in the echocardiography laboratory only after an AMI has been completely ruled out. The detection of jeopardized myocardium early after AMI can identify patients at a higher risk to develop subsequent events. In conclusion, echocardiography is cost effective in the triage of patients presenting with acute chest pain when performed soon after ED admission or during a chest pain episode. However, echocardiography must be readily available, expeditiously performed, and skillfully interpreted. The clinical use of stress echocardiography in acute coronary syndromes has been greatly improved with the introduction of digital and second harmonics technology and further enhanced by the availability of contrast agents.