title: Identification of factors predictive of lower extremity vein graft thrombosis.
abstract: OBJECTIVE
  The objective of this study was to assess the prognostic value of hemodynamic parameters measured with duplex ultrasound scan, together with other important graft and patient characteristics, in predicting lower extremity vein graft thrombosis.
  
  
  METHODS
  A total of 165 lower extremity vein grafts were entered prospectively into a postoperative duplex ultrasound scan surveillance program with examinations performed at 1, 2, 3, 4, 6, 9, 12, 18, and 24 months, and annually thereafter. Duplex scan-derived blood flow velocity measurements were recorded at 1562 patient visits over 7 years. Graft patency was determined after each visit, and an analysis of factors predictive of vein graft thrombosis 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 were 90%, 86%, and 79%, respectively. In multivariate analyses, duplex scan velocity measurements predictive of lower extremity graft thrombosis included 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 without 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 grafts with a of Vr of 3.5 or more (incidence rate ratio = 7.0; 95% CI, 3.4-14.6) or an MGV less than 50 cm/s (incidence rate ratio = 6.5; 95% CI, 3.3-13.1). In grafts without identifiable inflow, outflow, or graft stenoses, there was no association between MGV and the risk of graft thrombosis.
  
  
  CONCLUSIONS
  Duplex scan velocity measurements are valid predictors of impending 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 Vr of 3.5 or more, or inflow, outflow, or graft lesions associated with an MGV less than 50 cm/s are recommended. Grafts without detectable inflow, outflow, or graft stenoses, regardless of MGV, may be safely followed.
authors.affiliation: Department of Surgery (Vascular), University of Washington School of Medicine, Seattle, 98195-6410, USA. gibsonk@u.washington.edu
authors.forename: K D
authors.initials: KD
authors.lastname: Gibson
authors.forename: M T
authors.initials: MT
authors.lastname: Caps
authors.forename: D
authors.initials: D
authors.lastname: Gillen
authors.forename: R O
authors.initials: RO
authors.lastname: Bergelin
authors.forename: J
authors.initials: J
authors.lastname: Primozich
authors.forename: D E
authors.initials: DE
authors.lastname: Strandness
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity / Q000502:physiology; D019917:Blood Vessel Prosthesis Implantation; D005260:Female; D006083:Graft Occlusion, Vascular / Q000000981:diagnostic imaging / Q000209:etiology*; D006801:Humans; D007511:Ischemia / Q000000981:diagnostic imaging / Q000601:surgery*; D007866:Leg / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D018616:Ultrasonography, Doppler, Duplex; D014680:Veins / Q000637:transplantation