Identification of factors predictive of lower extremity vein graft thrombosis

Objective: The objective of this study was to assess the prognostic value o f hemodynamic parameters measured with duplex ultrasound scan, together wit h other important graft and patient characteristics, in predicting lower ex tremity vein graft thrombosis. Methods: A total of 165 lower extremity vein grafts were entered prospectiv ely into a postoperative duplex ultrasound scan surveillance program with e xaminations performed at 1, 2, 3, 4, 6, 9, 12, 18, and 24 months, and annua lly thereafter. Duplex scan-derived blood flow velocity measurements were r ecorded at 1562 patient visits over 7 years. Graft patency was determined a fter each visit, and an analysis of factors predictive of vein graft thromb osis was performed with Poisson regression. Results: Thirty-two episodes of first-time graft thrombosis occurred, 23 of which were permanent. One-, 3-, and 5-year secondary graft patency rates w ere 90%, 86%, and 79%, respectively. In multivariate analyses, duplex scan velocity measurements predictive of lower extremity graft thrombosis includ ed the maximum velocity ratio (Vr) in association with a graft stenosis and the mean graft peak systolic velocity (MGV) within nonstenotic portions of the body of the graft. The incidence of graft thrombosis among grafts with out inflow/outflow stenoses, with Vr less than 3.5, and with MGV 50 cm/s or more, was 2.9% per year. Incidence rates were considerably higher among gr afts with a of Vr of 3.5 or more (incidence rate ratio = 7.0; 95% CI, 3.4-1 4.6) or an MGV less than 50 cm/s (incidence rate ratio = 6.5; 95% CI, 3.3-1 3.1). In grafts without identifiable inflow, outflow, or graft stenoses, th ere was no association between MGV and the risk of graft thrombosis. Conclusion: Duplex scan velocity measurements are valid predictors of impen ding graft thrombosis. A Vr of 3.5 or more and an MGV less than 50 cm/s are the best predictive measures. Repair of correctable graft lesions with a V r of 3.5 or more, or inflow, outflow, or graft lesions associated with an M GV less than 50 cm/s are recommended. Grafts without detectable inflow, out flow or graft stenoses, regardless of MGV, may be safely followed.