Impact of attenuated plaque as detected by intravascular ultrasound on the occurrence of microvascular obstruction after percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction.

OBJECTIVES: The aim of the study was to investigate whether intravascular ultrasound (IVUS) can predict microvascular obstruction (MVO) as detected by magnetic resonance imaging (MRI) after primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI).

BACKGROUND: MVO occurs in a sizable proportion of patients with acute myocardial infarction despite successful PCI and results in poor clinical outcomes.

METHODS: We assessed infarct-related lesions in 68 patients with STEMI by using IVUS before primary PCI. All patients were examined by MRI 1 week after primary PCI.

RESULTS: MRI-derived MVO was seen in 23 patients (34%). In the IVUS assessment, the frequency of plaque rupture, echolucent plaque, calcification and positive remodeling, and quantitative geometric data were not different between the MVO group and the no-MVO group. Although the frequency of plaque with ultrasound attenuation was similar between the 2 groups (87% vs. 89%, p = 0.999), the maximum attenuation angle (280° [range: 215° to 360°] vs. 150° [range: 95° to 300°], p = 0.008) and attenuation length (11.3 mm [range: 7.2 to 17.8 mm] vs. 6.8 mm [range: 3.0 to 10.4 mm], p = 0.009) were significantly greater in the MVO group than the no-MVO group. Multivariable logistic regression analysis showed that attenuated plaque with a maximum attenuation angle of >180° and attenuation length of >5 mm was an independent predictor of MVO (odds ratio: 6.07, 95% confidence interval: 1.89 to 19.53, p = 0.002).

CONCLUSIONS: Attenuated plaque with maximum attenuation angle of >180° and attenuation length of >5 mm was associated with the occurrence of MVO after primary PCI. IVUS might to be a useful tool for risk stratification in STEMI patients undergoing primary PCI.