Presence and extent of cardiac magnetic resonance microvascular obstruction in reperfused non-ST-elevated myocardial infarction and correlation with infarct size and myocardial enzyme release.

OBJECTIVE: Microvascular obstruction (MO) is a factor of adverse outcome in patients with ST-elevated myocardial infarction (STEMI). We assessed the presence and extent of MO and its relationship with infarct size and left ventricular (LV) functional parameters after acute non-ST-elevated myocardial infarction (NSTEMI).
METHODS: Twenty-five patients with first acute NSTEMI underwent a cine and first-pass perfusion cardiac magnetic resonance (CMR) study, with late gadolinium enhancement imaging 72 h after myocardial infarction.
RESULTS: MO was detected in 32% of patients, and its extent comprised 0.5-3.1% of the total LV mass (mean 1.9 +/- 1.2%). Patients with MO had a significantly larger infarct size than patients without (14.1 +/- 5.9 vs. 5.3 +/- 4.1% LV mass; p < 0.001). There was no significant difference between both groups for the LV functional parameters and LV ejection fraction (58.5 +/- 6.8 vs. 62.6 +/- 9.6%; p = 0.29). Patients with MO showed a higher troponin I release (570 +/- 364 vs. 148 +/- 103 IU; p = 0.003) and a higher creatine kinase release (29,887 +/- 18,263 vs. 10,287 +/- 5,283 IU; p = 0.007).
CONCLUSIONS: In patients with acute NSTEMI, MO has a frequency similar to that observed in patients with STEMI and also correlates with the infarct extent. The prognostic significance on clinical outcome remains to be shown in this specific population. Copyright 2008 S. Karger AG, Basel.