248 Presence of endothelial colony-forming cells is associated with reduction of microvascular obstruction limiting infarct size and left ventricular remodelling: MRI study in acute myocardial infarction

BackgroundEndothelial colony-forming cells (ECFCs) have proliferative and vasculogenic capacities and can be detected in patients (pts) with myocardial infarction (MI). High ECFC levels reportedly lead to positive left ventricular (LV) remodelling after acute MI, but the mechanism of this improvement has never been assessed. We evaluated the relationship between ECFC levels and microvascular obstruction (MVO), and the impact of this relation on infarct size and LV remodelling at 6 months as assessed by magnetic resonance imaging (MRI).Methods109 pts<75 years old, admitted with a first MI within 12 hours of onset of symptoms were enrolled. Peripheral blood samples were drawn to assess number of ECFC colonies (culture cells). Measurements of infarct size by MRI were performed at day 5 and 6 months.ResultsECFC colonies were detected in 51/109 pts (47.2%) at admission (ECFCpos pts). At 5 days, MVO was more frequently observed (63% vs 33%; p = 0.003) and of greater magnitude (7 ± 6% vs 3 ± 5%, p = 0.0004) in ECFCneg patients versus ECFCpos pts respectively. At 6 months, there was a significantly greater reduction in infarct size in ECFCpos pts (−33.7 ± 33.2% vs −15.1 ± 24.6%, ECFCpos vs ECFCneg respectively; p = 0.003). This reduction in infarct size was associated with a significant improvement in LV ejection fraction and a significant reduction in LV end diastolic and systolic volumes in ECFCpos pts. A significant positive correlation was observed among ECFCpos pts between MVO at day 5 and infarct size at 6 months (r2=0.58, p<0.0001), while the number of ECFC colonies was significantly correlated with the relative change in infarct size at 6 months MRI (r2=0.33, p