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-infarct preserved microvascular integrity. Low dose dobutamine echocardiography and myocardial contrast echocardiography were used to study patients before hospital discharge who had suffered a recent myocardial infarction and had a patent infarct-related artery (TIMI flow grade 3). Method: In the dysfunctioning infarct area, the wall motion score index was calculated at baseline, during the dobutamine infusion and at the 3 month follow-up echocardiogram; contrast echocardiography was performed at the time of coronary angiography, before hospital discharge. Results: In patients with more than 50% of the dysfunctioning infarct area opacified at contrast echocardiography (group A), regional wall motion score index decreased, compared to baseline, during the dobutamine infusion (1.97 ± 0.78 vs 2.5 ± 0.35 at baseline; P <0.001) and at follow-up echocardiography (1.83 ± 0.63 vs 2.5 ± 0.35 at baseline; P <0.001). In patients with less extensive microvascular integrity as revealed by contrast echocardiography (group B), regional wall motion score index did not decrease from baseline during either the dobutamine 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 at baseline; P = ns). Conclusion: In patients with post-infarct dysfunctioning myocardium but a patent infarct-related artery, microvascular integrity, as assessed by myocardial contrast echocardiography, is an indicator of myocardial viability in terms of preserved contractile reserve, as demonstrated by dobutamine infusion and functional recovery at follow-up.