Risk factors for venous thromboembolism after vascular surgery and implications for chemoprophylaxis strategies

Abstract

Objective: Venous thromboembolism (VTE) is an important cause of postoperative morbidity and mortality. However, the reported incidence after major vascular surgery has ranged from as low as 1% to >10%. Furthermore, little is known about optimal chemoprophylaxis regimens or rates of postdischarge VTE in this population. In the present study, we aimed to better characterize the rates of in-hospital and postdischarge VTE after major vascular surgery, the role of chemoprophylaxis timing, and the association of VTE with mortality.

Methods: A single-center retrospective study of 1449 major vascular operations (2013-2020) was performed and included 189 endovascular abdominal aortic aneurysm repairs (13%), 169 thoracic endovascular aortic aneurysm repairs (12%), 318 open aortic operations (22%), 640 lower extremity bypasses (44%), and 133 femoral endarterectomies (9%). The baseline characteristics, anticoagulant and antiplatelet medications, and outcomes were abstracted from an electronic database with medical record auditing. Postoperative VTE (pulmonary embolism and deep vein thrombosis) within 90 days of surgery was classified by the location, symptoms, and treatment. A cut point analysis using Youden's index identified the most VTE discriminating timing of chemoprophylaxis (including therapeutic vs prophylactic anticoagulant and antiplatelet medications) and Caprini score. Multivariable logistic regression was used to test the association of VTE with chemoprophylaxis timing, Caprini score, and additional risk factors. Cox proportional hazard modeling was used to measure the association between VTE and mortality.

Results: The overall VTE incidence was 3.4% (65% deep vein thrombosis; 25% pulmonary embolism; 10% both), and 37% had occurred after discharge. The rate of symptomatic VTE was 2.4%, which was lowest for endovascular abdominal aortic aneurysm repair (0.0%) and highest for open aortic surgery (4.1%; P = .02). Those who had developed VTE had had a longer length of stay, higher rates of end-stage renal disease and prior VTE, and higher Caprini scores (8 vs 5 points; P < .01 for all). Those who had developed VTE were also more likely to have received ≥2 U of blood postoperatively, required an unplanned return to the operating room, had delayed chemoprophylaxis, anticoagulation, and/or antiplatelet initiation of >4 days postoperatively, and had increased 90-day mortality (P < .01 for all). A Caprini score of ≥7 (29% of patients) was associated with postdischarge VTE (2.6% vs 0.7%; P = .01), and chemoprophylaxis, anticoagulation, and antiplatelet timing of >4 days was associated with an increased adjusted odds of VTE (odds ratio, 2.4; 95% confidence interval, 1.1-4.9). Although no fatal VTEs were identified, VTE was an independent predictor of 90-day mortality (adjusted hazard ratio, 2.7; 95% confidence interval, 1.3-5.9).

Conclusions: These data have shown that patients undergoing major vascular surgery are particularly prone to the development of VTE, with frequent hypercoagulable comorbidities. The earlier initiation of chemoprophylaxis was associated with a reduced risk of VTE development. Furthermore, the postdischarge VTE rates might reach thresholds warranting postdischarge chemoprophylaxis, especially for patients with a Caprini score of ≥7.

Keywords: Perioperative care; Postoperative complications; Vascular surgical procedures; Venous thromboembolism.

Fig 1.

Rates of postoperative venous thromboembolism (VTE) across procedure types. Y-axis: VTE rate includes all VTEs (symptomatic and asymptomatic); black dotted line represents symptomatic VTE rate for each procedure. Data below each bar denote number of VTE events of total in each operative category. EVAR, Endovascular aortic aneurysm repair; Lower Ext Bypass, open lower extremity bypass; Open Aortic, open abdominal aortic aneurysm repair (n = 208) or aortobifemoral bypass (n = 110); TEVAR, thoracic endovascular aortic aneurysm repair.

Fig 2.

Rates of venous thromboembolism (VTE) stratified by Caprini score group. Odds ratios for association of Caprini score 7 to 9 and ≥10 groups with each outcome (all VTE and postdischarge VTE) shown at top of bars, with 2- to 6-point group as reference. Logistic regression results presented in Supplementary Table I (online only). P < .05 for all odds ratios displayed.

Fig 3.

Kaplan-Meier curves comparing survival ≤90 days for those with and without postoperative venous thromboembolism (VTE). Solid line indicates no VTE group (n = 1400; deaths, n = 67); dotted line, VTE group (n = 49; deaths, n = 10). Adjusted hazard ratio for VTE was 2.8 (P = .01). The results from the full Cox proportional hazard model are presented in Supplementary Table II (online only).