009 Impact of early vs late microvascular obstruction on ventricular remodeling at 6 months assessed by 3-Tesla magnetic resonance imaging in acute myocardial infarction

Abstract

Microvascular obstruction (MVO) at the acute phase of myocardial infarction (MI) is associated with greater myocardial damage, left ventricular (LV) impairment and higher mortality. We compared the impact of early and late microvascular obstruction (MVO) as assessed by 3-T cardiac magnetic resonance imaging (MRI) at the acute phase of MI on LV remodeling at 6 months. We included 51 consecutive patients (pts) with no previous history of cardiovascular disease, and presenting for first MI with or without ST elevation. Infarct size and extent of no-reflow were evaluated by 3-T MRI during acute phase by early and late hyperenhancement imaging at 3 and 15 min after gadolinium injection. Extent of no-reflow at 3 minutes (early MVO) and 15 minutes (late MVO) was measured. Follow-up MRI was performed at 6 months. Systolic and diastolic LV volumes, as well as LV ejection fraction and infarct size were compared at baseline and 6 months. Incidence of early MVO was 56% vs 43% for late MVO. There was a significant difference in extent of no-reflow between early and late MVO (7.8 ± 4% vs 5.4 ± 4%, p < 0.0001, early vs late respectively). There was also a significant difference in LV evolution at 6 months between pts with and without no-reflow (p < 0.05). In pts who showed no-reflow at 3 minutes only, but not at 15 minutes, ventricular dilatation was observed at 6 month follow-up of a magnitude similar to that observed in pts with persistent no-reflow at 15 minutes. Incidence of MVO is higher when assessed at 3 minutes, rather than at 15 minutes. In this context, systematic early MVO evaluation could help identify a larger group of pts at risk of unfavourable evolution, because when MVO is evaluated at 15 minutes, pts who had no-reflow at 3 minutes that subsequently resolved, go unidentified. The presence of MVO is associated with LV dilatation at 6 months follow-up, regardless of whether no-reflow was present at 3 minutes only, or persistent at 15 minutes.