Faculty Bibliography

OBJECTIVE:To determine the accuracy of detection of different tissue types of intravascular ultrasound-virtual histology (IVUS-VH) in a porcine model of complex coronary lesions. METHODS AND RESULTS/RESULTS:Coronary lesions were induced by injecting liposomes containing human oxidized low-density lipoprotein into the adventitia of the arteries. IVUS-VH imaging was performed in vivo at 8.2+/-1.6 weeks after injection. A total of 60 vascular lesions were analyzed and compared with their correspondent IVUS-VH images. Correlation analysis was performed using linear regression models. Compared with histology, IVUS-VH correctly identified the presence of fibrous, fibro-fatty, and necrotic tissue in 58.33%, 38.33%, and 38.33% of lesions, respectively. The sensitivity of IVUS-VH for the detection of fibrous, fibro-fatty, and necrotic core tissue was 76.1%, 46%, and 41.1% respectively. A linear regression analysis performed for each individual plaque component did not show strong correlation that would allow significant prediction of individual values. CONCLUSIONS:In a porcine model of complex coronary lesions, IVUS-VH was not accurate in detecting the relative amount of specific plaque components within each individual corresponding histological specimen.

BACKGROUND:Recent case control studies suggest that patients with subacute stent thrombosis (SAT) have increased platelet reactivity. However, SAT often presents as acute myocardial infarction (AMI), which is also associated with augmented platelet activation. We therefore compared platelet reactivity in patients with SAT and patients with AMI unrelated to stenting. METHODS:We identified 20 patients with SAT, 20 patients with ST-elevation AMI who underwent primary percutaneous coronary intervention (PCI), and 20 patients who underwent stenting without SAT occurrence (stable control group). Platelet function was measured > or = 3 days after PCI in the SAT (repeat procedure) and AMI groups and > or = 3 months after stenting in the stable group. All patients received aspirin and clopidogrel. Platelet reactivity was evaluated by aggregation in response to 5 and 20 micromol/L of adenosine diphosphate and 1.5 mmol/L arachidonic acid, and by flow cytometric determination of P-selectin and glycoprotein IIb/IIIa activation. RESULTS:Clinical characteristics were similar among the groups. Platelet testing was performed 4.9 +/- 1.7, 3.1 +/- 0.3, and 108 +/- 22 days after PCI in the SAT, AMI, and stable groups, respectively. The SAT group had higher platelet aggregation and activation markers than the stable group. However, platelet aggregation and activation was very similar in the SAT and AMI groups. CONCLUSIONS:Patients with SAT have increased platelet reactivity, compared with patients who do not develop SAT following stenting. However, the augmented platelet reactivity does not appear to differ from patients with AMI unrelated to stenting. This study highlights the need for large prospective studies to determine whether platelet hyperreactivity increases the risk of SAT.