Role of Echocardiography in Diagnosing Myocardial Ischemia at Emergency Department.

Because chest pain is one of the most common complaints that brings a patient to the emergency, the differential diagnosis of chest pain with or without acute coronary syndrome is very important. Traditionally, performing conventional echocardiography for detecting ischemia-related systolic abnormalities involves visually estimating the changes of wall thickening in circular muscle. This has well-documented limitations for both the interobserver variability and the ability of the human eye to resolve rapid, short-lived motion. Another approach to defining the regional myocardial properties could be to evaluate the deformation of a myocardial segment during the cardiac cycle. During the cardiac cycle, regional deformation of the myocardium occurs in 3 major directions: longitudinally; circumferentially; and radially. Currently, the terms “myocardial strain rate” and “strain” are used as indexes of longitudinal myocardial deformation. The physical definition of strain is the relative change in length of a material related to its original length. Regional strain rate and strain are derivative of myocardial velocities. The actual sequence of the regional changes in the myocardial function that are induced by acute ischemia has been well defined by experimental sonomicrometric techniques. Acute ischemia induces a delay in the onset of contraction, a progressive decrease in the rate and degree of thickening, and a progressive delay in the timing of the peak thickening until this event occurs in what is early diastole for the surrounding nonischemic myocardial segments. Finally, systolic thickening is virtually or completely abolished by total occlusion, and only late systolic/early diastolic thinning occurs. Although it has been well documented in the animal laboratory setting, all the components of the above ischemic response have yet to be well documented in the clinical setting by noninvasive imaging techniques. With the introduction of tissue Doppler imaging (TDI), pISSN 1975-4612 / eISSN 2005-9655 Copyright © 2017 Korean Society of Echocardiography www.kse-jcu.org https://doi.org/10.4250/jcu.2017.25.1.3