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Serial assessments of microvascular obstruction by contrast-enhanced magnetic resonance predict contractile recovery and clinical outcome after reperfused acute myocardial infarction.

AIMS
The purpose of the study was to investigate, using cardiac magnetic resonance (CMR), the presence and time course of microvascular obstruction (MO) in patients with acute myocardial infarction (AMI), and to test its relationship with cardiac remodeling and clinical outcomes.


METHODS AND RESULTS
53 patients with AMI and successful percutaneous reperfusion underwent CMR examination at four separate timepoints: within the first 48 hours, at 10 days, at six and twelve months after infarction. MO was quantified immediately (early imaging) and 10 minutes (late imaging) after contrast administration in each session. The extent of MO decreased from early to late imaging at both the first and the second CMR exam (p≤0.001). Early MO was absent in 18(36%) patients both at 48 hours and 10 days after AMI. At 1 year follow-up, LVEF in these patients improved to normal (median = 62% (53-70)). Early MO was present in the first but not in the second CMR in 13 (26%) patients; LVEF at one year in these patients reached a median = 52% (47-61). Finally, Early MO was present in both exams in 19 (38%) patients, who at 1 year after infarction had a LVEF of median = 49% (42-54, P≤0.001 across groups). The time course of MO was a predictor of prognosis upon Kaplan-Meier analysis (P = 0.035). The presence of MO at 10 days after AMI was associated with a higher risk of MACE during a 5-years follow-up.


CONCLUSIONS
The presence of MO within 48 hours after AMI, and its time course in the following ten days, provides complementary information on both functional myocardial recovery and long-term outcome.