Abstract 1746: MRI-determined Microvascular Obstruction and Infarct Size Express Accurately Reperfusion Injury and Predict Left Ventricular Function Recovery after Primary Coronary Angioplasty
Background: The aim of this study was to evaluate the relations between MRI-determined microvascular obstruction (MO) and infarct size (IS) and reperfusion injury following primary coronary angioplasty (PCI) in ST-elevation myocardial infarction (STEMI), and to assess the predictive value of IS and MO for left ventricular (LV) function recovery.
Methods: We evaluated 96 consecutive patients (aged 56.8 ± 11.5 y) with STEMI treated with PCI. A 1-year clinical follow-up was recorded. The magnetic resonance imaging (MRI) used as a method for the evaluation of MO and IS was performed 2– 4 days after STEMI by a 1.5-T MRI scanner. The following indexes were calculated: MO/LV and IS/LV. All patients were divided into three groups according to the size of MO: I. no MO (MO/LV = 0, n = 19), II. small MO (0 < MO/LV < 0.1, n = 46) and III. large MO (MO/LV ≥ 0.1, n = 31). A reperfusion injury was assessed by: (i) CK-MB release in the first 48 hours of reperfusion (AUC, Uxh) and (ii) ST-segment elevation resolution (STR) 1 hour after PCI. LV function recovery was evaluated by echocardiography 24 hours and 6 months after PCI and calculated on the basis of the changes (Δ) of ejection fraction (EF, %) and end-diastolic volume (EDV, ml).
Results: MO/LV was strongly correlated with STR (p < 0.001; r = 0.81), moderately correlated with EF (p = 0.015; r = −0.44) and not correlated with AUC at all. IS/LV was strongly correlated with AUC (p < 0.001; r = 0.69) and moderately correlated with EF (p = 0.006; r = −0.5). During a 6-month follow-up EF increased significantly in group I (Δ = 8.9; p = 0.04) and did not change significantly in group II (Δ = 4.8) and III (Δ = 0.9). EDV did not change significantly in group I (Δ = 5) and II (Δ = −5) but increased significantly in group III (Δ = 34ml, p = 0.02). After 1 year two persons in group II and three persons in group III died (p < 0.05 for I–III). A large MO was independently associated with a lack of EF improvement and EDV enlargement of >25 ml.
Conclusions: MRI-determined MO and IS were best correlated with routinely used STR and enzymatic injury respectively. The absence of MO was related to a mild myocardial injury and implicated a good microvascular integrity and a preserved LV function. In contrast, the large size of MO was associated with a major injury as well as with a poor LV function recovery.