Connection between the course of microvascular and infarct remodeling processes over time after reperfused ST-elevation acute myocardial infarction has not been fully elucidated. The aim of this study is to investigate the association of temporal changes in hemodynamics of microcirculation in the infarcted territory and infarct size (IS) after primary percutaneous coronary intervention in patients with ST-elevation acute myocardial infarction.

Thirty-five patients admitted with ST-elevation acute myocardial infarction undergoing primary percutaneous coronary intervention were enrolled in the study. Coronary flow reserve (CFR), index of microvascular resistance (IMR), and IS were assessed 2 days after primary percutaneous coronary intervention and at the 5-month follow-up. The predictors of the 5-month IS were the baseline values of IS (β=0.6, P<0.001), IMR (β=0.280, P=0.013), and CFR (β=−0.276, P=0.017). There were significant correlations between relative change in IS and relative change in measures of microvascular function (IS and CFR [r=−0.51, P=0.002]); IS and IMR ([r=0.55, P=0.001]). In multivariate model, relative changes in IMR (β=0.552, P=0.001) and CFR (β=−0.511, P=0.002) were the only predictors of relative change in IS. In patients with an improvement in IMR >33%, the mean IS decreased from 32.3±16.9% to 19.3±14% (P=0.001) in the follow-up. Similarly, in patients with an improvement in CFR >41%, the mean IS significantly decreased from 29.9±20% to 15.8±12.4% (P=0.003). But in patients with an improvement in IMR and CFR, which were below than the mean values, IS did not significantly decrease during the follow-up.

Improvement in microvascular function in the infarcted territory is associated with reduction in IS after reperfused ST-elevation acute myocardial infarction. This link suggests that further investigations are warranted to determine whether therapeutic protection of microvascular integrity results in augmentation of infarct healing.