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Factors Associated with Primary Vein Graft Thrombosis in a Multicenter Trial with Mandated Ultrasound Surveillance
Lawrence B. Oresanya, MD1, Gregory L. Moneta, MD2, Michael Belkin, MD3, Michael S. Conte, MD1.
1University of California San Francisco, San Francisco, CA, USA, 2Oregon Health and Science University, Portland, OR, USA, 3Brigham and Women's Hospital, Boston, MA, USA.
OBJECTIVE
The benefits of preventing lower extremity vein bypass graft (LEVBG) occlusion through duplex ultrasound (DUS) surveillance and timely re-intervention are established. However, even in the setting of surveillance a significant number of LEVBG become occluded as a first event. We sought to identify factors that may contribute to these primary occlusions using a multicenter clinical trial database.
METHODS
This was a retrospective analysis of the PREVENT III cohort of 1404 patients with critical limb ischemia who underwent LEVBG. Subjects were followed with DUS at regular intervals (1, 3, 6, 9, and 12 mos), with reintervention based on pre-specified DUS criteria. Patients who had graft occlusion as the initial graft-related event were identified; technical failures (adjudicated) were excluded. Multivariate analysis was used to identify predictors of primary graft occlusion.
RESULTS
Primary graft occlusion occurred in 200 subjects (14%), accounting for 34% of all initial graft-related events. Primary occlusion events were distributed throughout the postoperative year. Rates of recurrent CLI, loss of secondary patency, and major amputation in those with primary occlusion were 55%, 79% and 22% respectively as compared to 18%, 10% and 10% for the remaining cohort (p<0.001). On univariate analysis, African American race (HR 1.4 95%CI 1.01-1.9), use of anticoagulants (HR 1.54 95%CI 1.2-2), use of alternative/spliced vein conduit (HR 1.44 95%CI 1.1-1.97) and graft diameter <3mm (HR 1.97 95% CI 1.2-3.3) were associated with increased risk of primary occlusion. On multivariate analysis graft diameter <3mm (HR 1.8 95% CI 1.1-3) and use of anticoagulants (HR 1.4 95%CI 1.04-1.89) were independent predictors. In 110 subjects, DUS had revealed no critical threshold abnormalities prior to the thrombosis. On multivariate analysis graft diameter <3mm (HR 2.3 95%CI 1.2-4.7) was the sole independent predictor of these unheralded occlusions.
CONCLUSIONS
Approximately one-third of primary vein graft events are occlusions even in the setting of DUS surveillance. Smaller diameter grafts are at increased risk. These findings suggest that prevention of vein graft thrombosis requires further improvements in risk stratification, surveillance, and antithrombotic therapies.
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