The echocardiogram is a standard tool in the management of patients with acute myocardial infarction (MI). The role of echocardiography in establishing the diagnosis, location, and extent of MI, in diagnosing mechanical complications of infarction, and in providing prognostic information that is important for risk stratification will be reviewed. The use of transthoracic echocardiography for the evaluation of chest pain in the emergency department is discussed separately. (See "Transthoracic echocardiography for the evaluation of chest pain in the emergency department".)
DIAGNOSIS OF MI
The diagnosis of an acute myocardial infarction (MI) is typically based upon the history, electrocardiogram, and cardiac enzymes, particularly serum troponins and creatine kinase MB fraction (CK-MB). (See "Criteria for the diagnosis of acute myocardial infarction".) Although not routinely performed for diagnosis, echocardiography is an accurate, noninvasive test that is able to detect evidence of myocardial ischemia or necrosis.
A 2003 task force update of the 1997 American College of Cardiology, the American Heart Association, and the American Society of Echocardiography (ACC/AHA/ASE) guidelines for echocardiography recommended the use of echocardiography in the diagnosis of suspected acute ischemia or infarction not evident by standard means, but did not recommend echocardiography when the diagnosis was already apparent . Similarly, the 2011 appropriate use criteria for echocardiography classified use of echocardiography in the diagnosis of suspected MI as appropriate .
Severe ischemia produces regional wall motion abnormalities (RWMAs) that can be visualized echocardiographically within seconds of coronary artery occlusion (12±5 and 19±8 seconds in two series of patients evaluated during transient coronary occlusions induced by angioplasty) [3,4]. These changes occur prior to the onset of electrocardiographic changes or the development of symptoms (figure 1) . The RWMAs reflect a localized decrease in the amplitude and rate of myocardial excursion, as well as a blunted degree of myocardial thickening and local remodelling.
Since ischemic RWMAs develop prior to symptoms, chest pain in the absence of RWMAs should not be due to active myocardial ischemia. However, the converse is not true; the presence of RWMAs does not establish the diagnosis of ischemia. There are a number of other causes of RWMAs, including a prior infarction, focal myocarditis, prior surgery, left bundle branch block, ventricular preexcitation via an accessory pathway, and cardiomyopathy. (See "Transthoracic echocardiography for the evaluation of chest pain in the emergency department".)