Objectives: We evaluated the clinical significance of attenuated plaque (hypoechoic plaque with deep ultrasound attenuation).
Background: Attenuated plaques are unusual intravascular ultrasound (IVUS) findings in patients with acute coronary syndrome (ACS).
Methods: We reviewed clinical presentations and angiographic and pre-intervention IVUS findings in 293 ACS patients undergoing percutaneous coronary intervention (PCI) without a distal protection device: 187 with non-ST-segment elevation myocardial infarction (NSTEMI) and 106 with ST-segment elevation myocardial infarction (STEMI).
Results: Attenuated plaque was observed in 75 patients (25.6%): 39.6% of STEMI versus 17.6% of NSTEMI (p < 0.001). (We also reviewed 100 randomly selected patients with stable angina and pre-intervention IVUS; none had attenuated plaque.) Overall, in ACS patients with attenuated plaques: 1) the level of C-reactive protein was higher; 2) angiographic thrombus and initial coronary flow Thrombolysis In Myocardial Infarction flow grade <2 were more common; and 3) IVUS lesion site plaque burden and remodeling index were significantly greater, lesion site luminal dimensions significantly smaller, and thrombus, positive remodeling, and plaque rupture were more common. No-reflow (26.7% vs. 4.6%, p < 0.001) and deteriorated post-PCI coronary blood flow (8.0% vs. 2.8%, p = 0.001) were higher. In ACS patients with normal coronary blood flow at baseline, deterioration in the coronary blood flow post-PCI was more common in lesions with attenuated plaque.
Conclusions: Attenuated plaque was more common in ACS patients with STEMI than NSTEMI. Attenuated plaque in ACS patients was associated with a higher C-reactive protein level, more severe and complex lesion morphology, reduced coronary blood flow before PCI, and especially no-reflow after PCI.