Analysis of microvascular integrity, contractile reserve, and myocardial viability after acute myocardial infarction by dobutamine echocardiography and myocardial contrast echocardiography

The purpose of this study was to evaluate, in postinfarction dysfunctioning myocardium, the relative potential of myocardial contrast and low-dose dobutamine echocardiography in detecting myocardial viability, and the relation between microvascular integrity, contractile reserve, and functional recovery at follow-up. Twenty-four patients with recent myocardial infarction were studied before hospital discharge with low-dose dobutamine and myocardial contrast echocardiography. In the dysfunctioning infarct area, wall motion score index was calculated at baseline, during low-dose dobutamine, and at 3-month follow-up. Revascularization of the infarct-related artery was performed if clinically indicated. Eighteen patients (group A) had myocardial enhancement of the dysfunctioning infarct area at myocardial contrast echocardiography of >50%, whereas the remaining patients (group B) had an increase of ≤50%. Wall motion score index was similar at baseline in groups A and B (2.6 ± 0.4 and 2.8 ± 0.2; p = NS), but it improved during low-dose dobutamine and at follow-up only in group A (1.9 ± 0.9 and 1.9 ± 0.7, respectively; p < 0.001 vs baseline). In group B, wall motion score index was 2.7 ± 0.4 with low-dose dobutamine and 2.8 ± 0.2 at follow-up (p = NS vs rest). In identifying viable myocardial segments, myocardial contrast echo had 100% sensitivity and 46% specificity, whereas low-dose dobutamine echo had 71% sensitivity and 88% specificity. Thus, microvascular integrity after acute myocardial infarction is a fundamental prerequisite for ensuring myocardial contractile reserve and regional functional recovery. Myocardial contrast and low-dose dobutamine echocardiography have different, but complementary, diagnostic characteristics in detecting myocardial viability.