Background: Microvascular obstruction (MVO) is a cardiac magnetic resonance (CMR) marker of no-reflow in ST-segment elevation myocardial infarction (STEMI). It remains unresolved whether the infarct size corresponds only to the presence of MVO or also to its extent.
Methods: The study included 53 patients with first STEMI (median age 61.5 years, 77% male) treated with percutaneous coronary intervention (PCI) who underwent CMR after median 5 days from PCI. Small MVO was defined as patchy, non-confluent spots of dark areas of absent contrast surrounded by late gadolinium enhancement (LGE). Large MVO was defined as confluent areas of MVO comprising a large amount of the infarct zone.
Results: Microvascular obstruction was observed in 32 patients (60%) including 18 patients with small MVO (36%) and 14 patients with large MVO (24%). Patients with MVO were more likely to have TIMI 0/1 grade flow on initial angiogram, higher levels of necrotic markers, larger infarct size, larger left ventricular end-diastolic and end-systolic volume and lower ejection fraction in comparison to patients without MVO. These differences were not observed between patients with large and small MVO.
Conclusions: The presence of MVO but not its extent corresponds to larger infarct size in STEMI.
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