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PVSS4. Open-Cell vs. Closed-Cell Stent Design Differences in Blood Flow Velocities After Carotid Stenting

Damon S. Pierce, Eric B. Rosero, John G. Modrall, Rawson J. Valentine, George P. Clagett, Carlos H. Timaran.
University of Texas Southwestern Medical Center, Dallas, Texas.

OBJECTIVES: The differential effect of stent design, i.e., open-cell vs. closed-cell configuration, on carotid velocities detected by duplex ultrasonography (DUS) has not been established. To identify possible stent design differences in carotid velocities, we analyzed our experience with DUS obtained before and immediately after CAS.

METHODS: In a series of 141 CAS procedures performed over a 3-year period, data from postintervention DUS and carotid angiograms were evaluated for each patient. Peak systolic velocities (PSV), end-diastolic velocities (EDV), and internal carotid artery-to-common carotid artery (ICA:CCA) PSV ratios were compared according to stent design. Differences in carotid velocities were analyzed using parametric and nonparametric statistical tests.

RESULTS: Completion angiogram revealed successful revascularization and less than 30% residual stenosis in each case. The 30-day stroke-death rate in this series was 1.6% and was unrelated to stent type. Post-intervention DUS was obtained a median of 5 days after CAS (interquartile range [IQR], 1-25 days). Closed-cell stents were used in 41 cases (29%) and open-cell stents in 100 (71%). The median PSV was significantly higher for closed-cell stents (122 cm/s; IQR, 89-143 cm/s) than for open-cell stents (95.9 cm/s; IQR, 77.3-122.8)(p=.007). Median EDV (36 vs. 29 cm/s; p=.006) and median ICA:CCA PSV ratio (1.6 vs.1.2; P=.017) were also significantly higher for closed cell-stents. 44.7% of closed-cell stents had carotid velocities that exceeded the threshold of 50% stenosis by DUS criteria for a nonstented artery compared with 26.1% of open-cell stents (p=.04). After adjusting for carotid tortuosity and degree of residual stenosis, closed cell-stents had a 2.2-fold increased risk of showing abnormally elevated carotid velocities after CAS compared with closed-cell stents (odds ratio, 2.2; 95% confidence interval, 1.02-4.9).

CONCLUSIONS: Carotid velocities are disproportionately elevated after CAS with closed-cell stents compared with open-cell stents, which suggests that velocity criteria for quantifying stenosis may require modification according to stent design. The importance of these differences in carotid velocities related to stent design and the potential relationship with recurrent stenosis remains to be established.