Stent Thrombosis and Intrastent Thrombus Formation in Patients Undergoing Elective PCI: Results of an Angioscopic Substudy of the Randomized Trial PRASFIT-Elective (PRASugrel for Japanese PatIenTs with Coronary Artery Disease Undergoing Elective PCI)

Background: Angioscopy was performed in a group of patients in the PRASugrel For Japanese PatIenTs with Coronary Artery Disease Undergoing Elective PCI (PRASFIT-Elective) study to determine the incidence and clinical features of stent thrombosis. Stent thrombosis is an infrequent, but potentially severe event that may require revascularization or lead to other clinically significant events. Its incidence and clinical features in Japanese patients undergoing elective percutaneous coronary intervention (PCI) are poorly understood, especially in those receiving dual antiplatelet therapy with prasugrel or clopidogrel in combination with aspirin. Methods: Coronary angioscopy was performed before and at 36 weeks after elective PCI in 19 and 14 patients treated with prasugrel and clopidogrel, respectively, across eight participating institutions. Coronary angioscopic images were adjudicated by independent staff at a central laboratory to assess intrastent thrombus, neointimal coverage, and plaque color. Results: The proportion of stents with a red thrombus decreased from 57.9% (11/19) to 21.1% (4/19) in the prasugrel group (P = 0.0082) and from 50.0% (7/14) to 35.7% (5/14) in the clopidogrel group (P = 0.3173) at stenting to the follow-up visit. Platelet reactivity at 4 weeks was similar between patients with or without a red intrastent thrombus. Stent coverage was classified as Grade 1 in most of the patients, and the yellow plaque classification was Grade 0–2 in most of the patients. Conclusions: Prasugrel and clopidogrel were associated with low rates of red thrombus after 36 weeks of dual-antiplatelet therapy after PCI. Stent coverage and yellow plaque classification were similar in prasugrel- and clopidogrel-treated patients.