PB0917 - Long-term recurrence after subsegmental pulmonary embolism compared to more proximal pulmonary embolism - findings from the TROLL registry.

Background: Subsegmental pulmonary embolism (SSPE) refers to clots situated peripherally, obstructing exclusively the subsegmental arteries. Multi-detector computed tomography pulmonary angiogram (CTPA) has led to an increased detection of SSPE. However, there is limited data on the long-term recurrence of venous thromboembolism (VTE) after an episode of SSPE.

Aims: To determine the long-term incidence of VTE recurrence after cessation of anticoagulation in patients with SSPE in comparison to those with more proximal PE (non-SSPE), and to evaluate the 30-days all-cause mortality rate.

Methods: Between January 2005 and May 2020, 1371 patients with a first-time CTPA-verified PE without cancer were identified from The Venous Thrombosis Registry in ØstfOLd HospitaL (TROLL), Norway. PE cases were categorized into two groups: SSPE and non-SSPE. The 5-year cumulative incidence of recurrent VTE for SSPE and non-SSPE was calculated. Participants who provided signed informed written consent and deceased patients were included, as consent was waived for deceased patients by The Regional Committee for Medical and Health Research Ethics.

Results: 79 (5.8%) patients were diagnosed with SSPE, while 1292 (94.2%) had non-SSPE. Median age was 69 years (IQR 57-79), and 676 (49.3%) were women. 889 (64.8%) cases were categorized as unprovoked, with no differences between SSPE and non-SSPE groups (p=0.96). No difference was observed in the duration of anticoagulant treatment between the groups (SSPE 183 days vs. non-SSPE 184 days, p=0.25). The 5-year cumulative incidence of VTE recurrence was 10.0% (95% CI 2.2-39.5) for SSPE compared to 26.8% (95% CI 23.2-30.9) for non-SSPE (p=0.09). Furthermore, the 30-day cumulative mortality rate was 10.1% (95% CI 3.3-5.4) for SSPE and 3.9% (95% CI 3.0-5.1) for non-SSPE (p= 0.01).

Conclusion(s): While the VTE recurrence rate following SSPE was lower than in non-SSPE cases, it remained high, with 10% recurrence within 5 years. Unexpectedly, the 30-days mortality rate following SSPE was significantly higher compared to non-SSPE cases.