119: Microvascular obstruction assessed by 3-Tesla magnetic resonance imaging in acute myocardial infarction is correlated with plasma troponin I levels

Abstract

Infarct size is a powerful prognostic factor and is usually assessed indirectly using dosage of plasma levels of cardiac enzymes, particularly troponin. Microvascular obstruction (MVO) at the acute phase of myocardial infarction (MI) is associated with myocardial reperfusion injury, resulting in greater infarct size, left ventricular (LV) impairment and higher mortality. We aimed to evaluate whether a correlation exists between plasma levels of cardiac troponin I (cTnI) at the acute phase of MI and the extent of no-reflow as assessed by 3-T cardiac magnetic resonance imaging (MRI). Secondly, we aimed to define a cut-off value for cTnI predictive of no-reflow. We included 51 consecutive patients with no previous history of cardiovascular disease, and presenting for a first MI with ST elevation within the first 12 hours. Infarct size and extent of no-reflow were evaluated by 3-T MRI at day 5 using early and late hyperenhancement imaging at 3 and 15 minutes after injection of gadolinium. Extent of no-reflow at 15 minutes (MVO) was measured and correlated with repeat doses of cTnI on admission and at 6, 12, 24, 48 and 72 hours. At 6 months, a MRI was performed to evaluate the impact of MVO on LV remodeling. MVO was diagnosed in 29 patients (56%). Extent of MVO was significantly correlated to the peak troponin, to the repeat doses of cTnI (except the one on admission) and to the area under the curve for cTnI. Using Receiver-operating characteristic (ROC) curves analysis, a cut-off cTnI value >89 ng/mL at 12 hours seemed to best predict presence of early MVO with a sensitivity of 63% and a specificity of 88%. At 6 months follow up, MVO was associated with LV remodeling resulting in higher LV volumes and lower LV ejection fraction (LVEF). There is a relationship between plasma levels of cardiac troponin I (cTnI) at the acute phase of AMI and the extent of MVO as assessed by 3-T cardiac magnetic resonance imaging (MRI). A cut-off value of 89 ng/mL for cTnI at 12 hours seems to best predict presence of MVO, which contributes to LV remodeling.