Purpose: To determine the diagnostic accuracy of virtual histology intravascular ultrasound imaging (VH IVUS) of carotid plaque and to assess the feasibility of VH IVUS to identify plaque with embolic potential in patients undergoing carotid artery stenting (CAS).
Methods: Thirty patients (17 men; mean age 74+/-7 years) were entered nonrandomly into a single-center, prospective, 2-arm study following FDA and Institutional Review Board approval. In one arm, 15 patients underwent VH IVUS examination of carotid plaque with a cerebral protection device immediately followed by carotid endarterectomy (CEA). A comparison of "virtual" with true histology was then performed, classifying plaque type by VH IVUS and histopathology in a blinded study. In the second arm, 15 patients undergoing CAS had a preliminary VH IVUS scan performed with cerebral protection. Debris collected from the filter following stenting was examined histologically and compared with the VH IVUS data.
Results: The diagnostic accuracy of VH IVUS to agree with true histology in different carotid plaque types was 99.4% in thin-cap fibroatheroma, 96.1% for calcified thin-cap fibroatheroma, 85.9% in fibroatheroma, 85.5% for fibrocalcific, 83.4% in pathological intimal thickening, and 72.4% for calcified fibroatheroma. Filter debris was captured in 2 patients prior to CEA and in 4 patients undergoing CAS for restenosis; VH IVUS classification of plaque composition was consistent with the histological evaluation of filter fragments. Calcified nodules projecting into the carotid artery lumen were associated with a higher incidence of previous neurological symptoms (66.7% versus 33.3%, p<0.05), while patients on aspirin has significantly less necrotic lipid core plaque detected by VH IVUS than patients not taking aspirin (6.4%+/-4.7% versus 9.7%+/-2.8%, p<0.05).
Conclusion: This study showed a strong correlation between VH IVUS plaque characterization and the true histological examination of the plaque following endarterectomy, particularly in "vulnerable" plaque types. The feasibility study to examine VH IVUS data and the filter debris histology in CAS patients supports a larger prospective study.