The role of Dobutamine stress echocardiography in the assessment of myocardial viability in patients with ischemic left ventricular dysfunction

Abstract

Introduction: Stress (exercise or pharmacologic) two-dimension transthoracic echocardiography can be used to demonstrate the presence of coronary disease, to assess myocardial viability prior to revascularization, to identify “culprit” lesion, etc. Impaired left ventricular (LV) systolic function in patients with coronary heart disease is often a partially reversible process and it may improve markedly, and even normalize, in subsets of patients following successful revascularization. The myocardium that recovers function after revascularization has been called "hibernating". To the extent that improvement in regional or global LV systolic function is a significant goal in such patients, the ability to accurately assess regional myocardial viability in a dysfunctional territory prior to revascularization becomes an important component of the decision making process. Purpose and Objectives: The role of Dobutamine stress echocardiography (DSE) in the evaluation of myocardial viability in the setting of hibernation will be reviewed here. Material and Methods: The analysis of the available literature about the importance and clinical application of Dobutamine stress echocardiography in the assessment of myocardial viability. Results: DSE is an important noninvasive clinical tool for the detection of hibernating myocardium. It examines the "inotropic reserve" of dysfunctional but viable myocardium. A contractile response to Dobutamine appears to require that at least 50 percent of the myocytes in a given segment are viable; the contractile response also correlates inversely with the extent of interstitial fibrosis on myocardial biopsy. The predictive value of Dobutamine stress echocardiography appears to be greatest when there is a biphasic response: improvement at low dose and worsening at high-dose Dobutamine. The initial improvement in wall motion reflects recruitment of contractile reserve during low-dose Dobutamine, and hence reflects viability. In comparison, higher doses lead to subendocardial ischemia and worsening of the wall motion abnormality, identifying stress-induced ischemia. Thus, testing at various doses appears to be important for the optimal assessment of myocardial hibernation by this technique. Patients with left ventricular dysfunction who demonstrate myocardial viability with Dobutamine stress echocardiography have a better survival with revascularization than with medical therapy. Conclusion: The available data strongly suggests that DSE studies help differentiate viable from nonviable myocardium, and identify patients with ischemic LV dysfunction that will most likely benefit from coronary revascularization.