Post-Procedure Duplex-Calculated Blood Flow Measurements Correlate To Stent Patency At 12 Months

OBJECTIVES: The utility of Duplex surveillance of arterial stents has been controversial, primarily aimed at detecting in-stent restenosis. While velocities are commonly reported, they do not represent blood flow. The patency of arterial prostheses is flow-dependant. We performed a preliminary evaluation of consecutive patients to determine if post-procedure, calculated blood flows through stents correlate to their 12 month primary patency.
METHODS: A retrospective review of consecutive patients undergoing arterial stent placement was performed. Information regarding demographics, comorbidities, stent size, post-procedure duplex information, and 12 month patency were recorded. Blood flow was calculated using duplex velocities and stent dimensions.
RESULTS: 27 consecutive patients (72.6±14 yrs., 14 male) were studied representing 35 stents (18 iliofemoral, 10 carotid, 7 subclavian/mesenteric). Mean time from procedure to duplex study was 47 days. 20 stents were primarily patent (PP) and 15 were secondarily patent (SP) at 12 months. There was a significant difference between the PP and SP groups with respect to initial, in-stent mean velocities and calculated flows. (92.5 cm/sec PP vs. 43.7 cm/sec SP, p<0.002; 1918 ml/min PP vs. 722 ml/min SP, p<0.0001) Using these threshold values, calculated flows had corresponding sensitivity, specificity, and accuracy of 92%, 82%, and 86.2% respectively for predicting stent patency while those for velocity measurements were lower at 83%, 71%, and 76% respectively. ROC curve (Fig. 1) analysis showed a significantly greater AUC for calculated flows compared to velocity measurements. (0.965 vs. 0.859, p<0.001) CONCLUSIONS: Calculated blood flows from an initial post-procedure duplex study accurately correlate to stent patency at 12 months. Velocities alone were less sensitive, less specific, and less accurate as measured by ROC analysis. This preliminary finding mandates prospective analysis of this technique with individual vascular beds and larger patient populations. A clinical protocol guiding stent surveillance and decisions for early reintervention is suggested.