The Relationship Between Attenuated Plaque Identified by Intravascular Ultrasound and No-Reflow After Stenting in Acute Myocardial Infarction: The HORIZONS-AMI (Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction) Trial

Study Questions:

What is the impact of attenuated plaque on distal embolization during stent implantation in patients with acute myocardial infarction (AMI)?


The investigators analyzed clinical, angiographic, and intravascular ultrasound (IVUS) data from 364 patients (n = 364 infarct-related arteries) enrolled in the randomized HORIZONS-AMI trial. No-reflow was final Thrombolysis In Myocardial Infarction (TIMI) flow grade 2 in the absence of mechanical obstruction. Attenuated plaque was hypoechoic or mixed atheroma with ultrasound attenuation without calcification. A mean attenuation score was created by measuring the angle of attenuation each 1 mm, scoring the angle as 1-4 (corresponding to <90°, 90-180°, 180-270°, or 270-360°, respectively), summing the scores, and normalizing for analysis length. A stepwise multivariate logistic regression analysis was conducted to identify independent predictors of no-reflow.


Overall, 284 (78.0%) patients had attenuated plaques; no-reflow occurred in 37 (10.2%). Patients with no-reflow had a higher mean attenuation score (median [interquartile range] 2.2 [0.0-2.8] vs. 1.3 [0.7-1.8], p < 0.001), lower baseline left ventricular ejection fraction (52.8% [43.2-61.5%] vs. 61.4% [52.2-68.1%], p = 0.002), and more baseline angiographic thrombus (89.2% vs. 74.1%, p = 0.043) with no differences in post-percutaneous coronary intervention (PCI) stent expansion versus patients without no-reflow. Multivariate analysis indicated that mean attenuation score was the strongest predictor of no-reflow. The mean attenuation score that best predicted no-reflow was 2 points (90-180°, sensitivity of 81.5%, and specificity of 80.5%).


The authors concluded that the amount of attenuated plaque strongly correlated with no-reflow.


The study suggests that attenuated plaque is present in three-quarters of patients with AMI. Furthermore, the extent of the attenuation rather than its mere presence is strongly correlated with no-reflow; the larger the attenuated plaque, the greater the likelihood of no-reflow. Attenuated plaques represent a large amount of necrotic core containing fragile tissues such as lipid deposition with foam cells, cholesterol crystals, and microcalcifications that are easily embolized by mechanical fragmentation during coronary stenting, and the current study extends previous observations that large attenuated plaques might be more likely to embolize spontaneously before PCI as well as after balloon dilation and stent implantation.

Clinical Topics: Invasive Cardiovascular Angiography and Intervention

Keywords: Myocardial Infarction, Plaque, Atherosclerotic, Stents, Percutaneous Coronary Intervention

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