Xiaofan Wu1; Akiko Maehara1; Gary S Mintz1; Alexandra J Lansky1; Bernhard Witzenbichler2; Giulio Guagliumi3; Bruce Brodie4; Mirle A Kellett， Jr5; Helen Parise6; Roxana Mehran6; Gregg W Stone6
    1 Cardiovascular Rsch Foundation， New York， NY
    2 Charite Univ Medicine Campus Benjamin Franklin， Germany， Franklin， Germany
    3 Ospedali Riuniti di Bergamo， Italy， Bergamo， Italy
    4 LeBauer CV Rsch Foundation/Moses Cone Hosp， Greensboro， NC
    5 Maine Med Cntr， ME， Poland
    6 Cardiovascular Rsch Foundation， New York， NY
    Background: Observational studies have suggested that attenuated plaques identified by grayscale intravascular ultrasound (IVUS) may predict transient deterioration in flow during percutaneous coronary intervention (PCI). If so， this phenomenon would be expected to be noted in pts undergoing primary PCI for STEMI.
    Methods and Results: We analyzed clinical， angiographic and IVUS characteristics of infarct related arteries of 365 stented pts from the randomized HORIZONS-AMI trial. No-reflow was defined as final TIMI grade 0， 1 or 2 flow in the absence of a mechanical obstruction on the post-PCI angiogram. Attenuated plaque was defined as hypoechoic or mixed atheroma with ultrasound attenuation without calcification. A mean attenuation score was created by measuring the angle of attenuation each 1mm， scoring as 1， 2， 3， or 4 when the angle was <90°， 90 –180°， 180–270°， or 270–360°， respectively， then summing the scores and normalizing for analysis length. 77.8% pts had attenuated plaques， and no-reflow occurred in 10.1%. Pts with no-reflow more often had PCI of a LAD than non LAD (59.5% vs 36.9%， P=0.03) and had a higher mean attenuation score (median [95%CI]=2.2 [0， 2.8] vs 1.3 [0.6， 1.8]， P<0.001). There were no differences in baseline thrombus area， IVUS plaque burden， echolucent plaque， and stent expansion between pts with vs without no-reflow. The mean attenuation score that best predicted no-reflow was  2 (90–180°)， with a sensitivity of 81.5% and a specificity of 80.5%.
Conclusions: Attenuated plaque is present in three-quarters of pts with AMI， PCI of which is strongly correlated with no reflow. The larger the attenuated plaque， the greater the likelihood of no-reflow.

 
Figure Attenuation angle: 125°
Attenuation score: 2 points