Abstract 125: Intravascular Ultrasound: A Clinically Useful Tool for Carotid Plaque Characterization

OBJECTIVE: Virtual Histology Intravascular Ultrasound (VH™ IVUS) is valuable for estimating minimal lumen diameter (MLD) and plaque characterization. The clinical use of IVUS in the carotid arteries is not well characterized. To evaluate carotid plaque morphology, we performed VH™ IVUS in patients with known carotid artery stenosis. METHODS: From July 2010, patients were prospectively enrolled in an IRB approved study to undergo IVUS prior to an elective carotid stenting procedure. Hospital records were reviewed for co-morbidities, carotid/arch anatomy, preoperative carotid duplex velocity measurements, and incidence of postoperative microemboli. Comparison of pre- and postoperative diffusion-weighted MR images was used to identify microemboli. IVUS-derived MLD and vessel wall plaque characteristics were collected. Spearman correlation was performed between MLD and duplex estimated stenosis, and between plaque characteristics and frequency of postoperative microemboli. RESULTS: 14 patients were enrolled during the study period with carotid artery stenosis (average ICA/CCA ratio 5.5, 64.3% asymptomatic). Major co-morbidities included hyperlipidemia (79%), diabetes (71%), and angina (43%). 57% of patients had type 1 arches, and 50% of patients had heavily calcified irregular carotid plaques. MLD correlated with preoperative duplex ICA/CCA ratio (R2=-0.56,p=0.05), and carotid plaque area correlated with peak systolic and diastolic velocities (R2=-0.55,p=0.05). Although microembolic frequency did not correlate with preoperative patient characteristics, it correlated with IVUS-derived plaque necrotic core area (R2=0.53,p=0.05). CONCLUSION: We demonstrate that periprocedural carotid IVUS is clinically feasible and useful. Preoperative duplex measurements correlated with IVUS MLD confirming the fidelity of the technique. Moreover carotid IVUS demonstrates that patients with necrotic plaque cores have a higher frequency of postoperative microemboli. These findings suggest that carotid IVUS may be helpful to identify patients who are at higher risk of microemboli during carotid artery stenting.