Long-term recurrence, bleeding, and mortality after first-time subsegmental pulmonary embolism compared to more proximal pulmonary embolism: Findings from the TROLL registry

Background: Subsegmental pulmonary embolism (SSPE) refers to clots that exclusively obstruct the subsegmental arteries. Data on long-term recurrence and bleeding risks following SSPE remain limited. Objectives: To determine the long-term incidence of venous thromboembolism (VTE) recurrence after cessation of anticoagulation in patients with SSPE compared to those with more proximal PE (non-SSPE), to assess major and clinically relevant non-major bleeding (CRNMB), and to evaluate 30-day and 31-365-day all-cause mortality. Methods: Between January 2005 and May 2020, 1135 cancer-free patients with a first-time computed tomography-verified PE were identified from The Venous Thrombosis Registry in & Oslash;stfOLd HospitaL (TROLL), Norway. Results: Among the 1135 patients, 72 (6.3 %) were diagnosed with SSPE, while 1063 (93.7 %) had more proximal PE. Median age was 70 years (IQR: 58-80), and 51.4% were women. The 10-year cumulative incidence of VTE recurrence after discontinuation of anticoagulation was 16.5 % (95 % CI: 4.5-35.1) in the SSPE group compared to 28.4 % (95 % CI: 24.5-32.4) in the non-SSPE group (p = 0.08). The 6-month cumulative incidence of major bleeding was 1.4% (95% CI, 0.1-6.6) in SSPE cases and 4.6% (95% CI: 3.4-5.9) in non-SSPE cases (p = 0.23). The 30-day all-cause mortality rate was 9.7 % (95% CI: 4.8-19.3) for SSPE and 4.4% (95 % CI: 3.3-5.8) for non-SSPE (p = 0.04). Conclusion: While the VTE recurrence rate following SSPE was lower than in non-SSPE cases, it remained high, with 16.5 % recurrence within 10 years. Major bleeding rate was lower for SSPE than non-SSPE (1.4% vs. 4.6%, p = 0.23). Unexpectedly, the 30-days mortality rate following SSPE was significantly higher compared to non-SSPE cases.