End to End Proximal Anastomosis is the Sole Modifiable Variable in Risk Score for Loss of Patency of Aortobifemoral Artery Bypass After Index Operative Hospitalization.

OBJECTIVE: The purpose of this study was to create a risk score for loss of aorto-bifemoral artery bypass (ABF) patency utilizing preoperative, perioperative, and long term follow up variables in the Vascular Quality Initiative (VQI) database. METHODS: The VQI supra-inguinal arterial bypass module was queried from 2009-2025 and 4971 patients undergoing ABF had long term follow patency data and thus met inclusion. These patients were then divided into a 2/3 testing cohort (N=3364) and a 1/3 validation cohort (N=1607) on whom the risk score would be trialed. The first step was univariable analysis for the outcome of loss of patency of either or both ABF limbs after elective ABF with Chi-squared testing for categorical variables. The 67% testing cohort was used for this initial analysis. Demographics, socioeconomics, and co-morbidities that were hypothesized to have any potential association with bypass occlusion were selected for the initial univariable analysis. Next, multivariable Cox regression time dependent analysis was performed for the outcome of thrombosis of either ABF limb utilizing factors which had a univariable P value of 0.05 or less. Variables with a multivariable P-value < .05 from the above-mentioned regression were included in the risk score and weighted based on their respective regression beta-coefficient in a point scale. Variables with a beta-coefficient of less than .25 were assigned 1 point, and then a point was added for each rise in beta-coefficient at .25 intervals. Machine learning (ML) supplemental analysis with IBM modeler software was also performed. RESULTS: Multivariable Cox regression analysis for the development of ABF thrombosis after index operative hospitalization utilizing significant univariable factors found multivariable significance (P<.05) and ultimate inclusion in the risk score for : operative site infection after discharge (hazard ratio [HR] 1.84, P=.038); revision to achieve primary assisted patency (open or endovascular) in follow up (HR 7.14, P<.001); ischemic tissue loss at initial operation (HR 2.29, P<.001); and either femoral outflow target artery being less than 8mm in diameter (HR 1.59, P<.001). End to end proximal aortic anastomosis was protective (HR .568, P=.003) as was patient not being selected for anticoagulation medication at the time of most recent long-term follow-up (LTFU; HR .731, P<.001). Patients who fell into risk score bundle #1 (raw scores <0) experienced the primary event in 2.1% of cases. Patients in risk score bundle #2 (raw scores 0 - 5) had a 5% event rate and patients in risk score bundle #3 (raw score >5) experienced graft thrombosis at a 44.8% risk. There was thus statistically significant escalation in event rate with rising risk score (P<.001). Receiver operator characteristics for the risk score revealed an area under the curve (AUC) value of .733. There was no significant difference in primary event rate between the testing and validation cohorts at any of the risk score bundles. The top ML methodology achieved an AUC of .914 and confirmed all the Cox regression significant multivariable factors (including end to end anastomosis) to be of high importance. CONCLUSIONS: A validated risk score for the event of ABF occlusion after index operative hospitalization has been developed. Performing an end-to-end proximal aortic anastomosis when not anatomically contra-indicated should be considered to enhance long term patency. Anatomic and disease pattern variables weigh most heavily on patency.