Factors Associated With Primary Vein Graft Thrombosis in a Multicenter Trial With Mandated Ultrasound Surveillance

Abstract

The benefits of preventing lower extremity vein bypass graft (LEVBG) occlusion through duplex ultrasound (DUS) surveillance and timely reintervention 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. This was a retrospective analysis of the PREVENT III cohort of 1404 patients with critical limb ischemia who underwent LEVBG. Participants were followed up with DUS at regular intervals (1, 3, 6, 9, and 12 months), with reintervention based on prespecified DUS criteria. Patients who had graft occlusion as the initial graft-related event were identified, and technical failures (adjudicated) were excluded. Multivariate analysis was used to identify predictors of primary graft occlusion. Primary graft occlusion occurred in 200 participants (14%), accounting for 34% of all initial graft-related events. Primary occlusion events were distributed throughout the postoperative year. Rates of recurrent critical limb ischemia, loss of secondary patency, and major amputation in those with primary occlusion were 55%, 79%, and 22%, respectively, compared with 18%, 10%, and 10% for the remaining cohort (P < .001). On univariate analysis (hazard ratio [HR] [95% confidence interval]), African American race (1.4 [1.01-1.9]), use of anticoagulants (1.54 [1.2-2]), use of alternative/spliced vein conduit (1.44 [1.1-1.97]) and graft diameter <3 mm (1.97 [1.2-3.3]) were associated with increased risk of primary occlusion. On multivariate analysis (HR [95% confidence interval]) graft diameter <3 mm (1.8 [1.1-3]) and use of anticoagulants (1.4 [1.04-1.89]) were independent predictors. In 110 individuals, DUS had revealed no critical threshold abnormalities prior to the thrombosis. On multivariate analysis, graft diameter <3 mm (2.3 [1.2-4.7]) was the sole independent predictor of these unheralded occlusions. 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.