Impaired coronary flow reserve after a recent myocardial infarction: Correlation with infarct size and extent of microvascular obstruction

Background: The exact relationship between the coronary flow reserve (CFR) and infarct size remains unknown. In this prospective study the relationship between the CFR both in the infarcted and remote myocardium and infarct size was investigated. Furthermore, the diagnostic value of the CFR to predict the extent of microvascular obstruction (MO) was evaluated. Methods: In thirty patients the CFR was measured with a Doppler guide wire 6 ± 3 days after a first myocardial infarction (MI) in the infarct related and in a reference coronary artery. MO and infarct size were determined with magnetic resonance imaging. Results: The CFR was inversely related to infarct size in the infarcted and remote myocardium (respectively, r= -0.60, p<0.01 and r= -0.62, p<0.01). In the infarcted myocardium the extent of MO was strongly related to the infarct size and was in a multivariate analysis the single significant determinant of the CFR and the hyperaemic flow. In the remote myocardium no relationship was present between infarct size and hyperaemic flow, but the baseline flow increased as the infarct size became larger (r=0.58, p<0.01). In a receiver operator characteristic (ROC) analysis, a CFR value≤2 in the infarct related coronary artery offered the best sensitivity (65%) and specificity (71%) to detect the presence of MO (p<0.05). Conclusions: After MI, the CFR both in the infarcted and remote myocardium is inversely related to infarct size. In the infarcted myocardium, a CFR value ≤2 predicts the presence of MO with moderate sensitivity and specificity.