Antiphospholipid syndrome and late pulmonary thrombosis after pulmonary endarterectomy

OBJECTIVES: To determine the prevalence of antiphospholipid syndrome in surgical chronic thromboembolic pulmonary hypertension and its association with late in situ pulmonary artery thrombosis after pulmonary endarterectomy. METHODS: Retrospective cohort of 220 patients undergoing pulmonary endarterectomy at a single centre (2015-2024). Antiphospholipid syndrome was diagnosed per 2006 Sydney criteria with confirmatory antibody testing ≥12 weeks apart. The primary outcome was in situ pulmonary artery thrombosis on follow-up computed tomography pulmonary angiography. Survival and logistic regression analyses were performed. RESULTS: Antiphospholipid syndrome was identified in 36 patients (16.4%), who were younger (40.2 vs 50.2 years; P=.001) and had more prior deep vein thrombosis (69.4% vs 48.9%; P=.038). Over a median 70.5-month follow-up, in situ pulmonary artery thrombosis was more frequent with antiphospholipid syndrome (36.1% vs 15.2%; relative risk 2.37; P=.008). Ten-year recurrence-free survival was 64% versus 82% (log-rank P=.002). Univariate odds ratio was 3.15 (95% confidence interval 1.43-6.94; P=.004); after adjustment for age, sex, and prior deep vein thrombosis, adjusted odds ratio was 2.22 (0.95-5.18; P=.064). Triple-positive patients (n = 6) had 83.3% in situ pulmonary artery thrombosis versus 26.7% in other antiphospholipid syndrome patients (P=.016; absolute risk difference 56.7 percentage points), a hypothesis-generating finding. CONCLUSIONS: Antiphospholipid syndrome is associated with elevated late in situ pulmonary artery thrombosis after pulmonary endarterectomy. The adjusted association was borderline. Triple positivity warrants validation in larger cohorts. Preoperative antibody testing may inform surveillance.