Functional role of microvascular integrity in patients with infarct-related artery patency after acute myocardial infarction

AIMS: The study was set up to evaluate the functional role of post-infarctpreserved microvascular integrity. Low dose dobutamine echocardiographyand myocardial contrast echocardiography were used to studypatients before hospital discharge who had suffered a recentmyocardial infarction and had a patent infarct-related artery(TIMI flow grade 3). METHOD: In the dysfunctioning infarct area, the wall motion score indexwas calculated at baseline, during the dobutamine infusion andat the 3 month follow-up echocardiogram; contrast echocardiographywas performed at the time of coronary angiography, before hospitaldischarge. RESULTS: In patients with more than 50% of the dysfunctioning infarctarea opacified at contrast echocardiography (group A), regionalwall motion score index decreased, compared to baseline, duringthe dobutamine infusion (1·97 ± 0·78 vs2·5 ± 0·35 at baseline; P<0·001)and at follow-up echocardiography (1·83 ± 0·63vs 2·5 ± 0·35 at baseline; P<0·001).In patients with less extensive microvascular integrity as revealedby contrast echocardiography (group B), regional wall motionscore index did not decrease from baseline during either thedobutamine infusion (2·73 ± 0·21 vs 2·81± 0·20 at baseline; P=ns) or at follow-up (2·81± 0·20 vs 2·81 ± 0·20 atbaseline; P=ns). CONCLUSION: In patients with post-infarct dysfunctioning myocardium buta patent infarct-related artery, microvascular integrity, asassessed by myocardial contrast echocardiography, is an indicatorof myocardial viability in terms of preserved contractile reserve,as demonstrated by dobutamine infusion and functional recoveryat follow-up.