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Subsegmental PE – Small But Significant?

January 11, 2022

Essentials of Emergency Medicine Education Fellowship

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Written by Sam Parnell and Bo Stubblefield

Spoon Feed
Patients with single and multiple isolated subsegmental pulmonary embolism (SSPE) without proximal deep venous thrombosis (DVT) managed without anticoagulation had an incidence of recurrent venous thromboembolism (VTE) of 3.1% (95% CI, 1.6% to 6.1%) within 90 days.  This incidence of recurrent VTE was higher than expected and has implications for management of these patients with anticoagulation.

Why does this matter?
The incidence of PE in both the US and Europe has increased in the last two decades, while the case-fatality rate has decreased (1-3). The widespread use of computed tomography pulmonary angiography has led to increased diagnosis of isolated SSPE (4). However, the clinical significance of SSPE remains unknown. Although current guidelines suggest clinical surveillance over anticoagulation in select patients with SSPE, there is only low-level evidence to guide this recommendation (5). Are these patients at low risk for recurrent VTE who simply need clinical surveillance, or is anticoagulation indicated?

SSPE: Small but significant?
This was a multicenter, international, prospective cohort study evaluating clinical outcomes for low-risk patients with single and multiple isolated SSPE managed without anticoagulation. Patients diagnosed with isolated SSPE had bilateral lower extremity ultrasound, and patients with no DVT on ultrasound were managed without anticoagulation. Patients who were hospitalized, pregnant, had active cancer, a history of VTE, hypoxia, or an indication for long term anticoagulation were excluded.

Recruitment in the study ended early because the predefined stopping rule was met after 292 of the projected 300 patients were enrolled. Overall, 266 patients were included in the study. The primary outcome of recurrent VTE during the 90-day follow-up period occurred in 8 patients with a cumulative incidence of 3.1% (95% CI, 1.6% to 6.1%). This incidence rate was higher than expected but similar to a prior systematic review of patients with more proximal pulmonary embolism receiving anticoagulation (6).

Patients with multiple isolated SSPE had higher incidence of recurrent VTE compared to those with single isolated SSPE (5.7% vs 2.1%, respectively), and patients >65 years had higher rate of recurrent VTE compared to those ≤65 years (5.5% vs 1.8%). In total, 4 patients had recurrent proximal PE and 4 patients had DVT. No patients had a fatal recurrent PE. This increased incidence of recurrent VTE should be taken into account, along with co-morbidities, bleeding risk, and patient values, when considering the use of anticoagulation for patients with SSPE.

Risk for Recurrent Venous Thromboembolism in Patients With Subsegmental Pulmonary Embolism Managed Without Anticoagulation : A Multicenter Prospective Cohort Study. Ann Intern Med. 2021 Nov 23. doi: 10.7326/M21-2981. Online ahead of print.


  1. Bikdeli B, Wang Y, Jimenez D, et al. Pulmonary Embolism Hospitalization, Readmission, and Mortality Rates in US Older Adults, 1999-2015. Jama 2019;322:574-6.

  2. Keller K, Hobohm L, Ebner M, et al. Trends in thrombolytic treatment and outcomes of acute pulmonary embolism in Germany. European heart journal 2020;41:522-9.

  3. Lehnert P, Lange T, Moller CH, Olsen PS, Carlsen J. Acute Pulmonary Embolism in a National Danish Cohort: Increasing Incidence and Decreasing Mortality. Thrombosis and haemostasis 2018;118:539-46.

  4. Wiener RS, Schwartz LM, Woloshin S. Time trends in pulmonary embolism in the United States: evidence of overdiagnosis. Arch Intern Med 2011;171:831-7.

  5. Kearon C, Akl EA, Ornelas J, et al. Antithrombotic Therapy for VTE Disease: CHEST Guideline and Expert Panel Report. Chest 2016;149:315-52.

  6. Carrier M, Le Gal G, Wells PS, Rodger MA. Systematic review: case-fatality rates of recurrent venous thromboembolism and major bleeding events among patients treated for venous thromboembolism. Ann Intern Med 2010;152:578-89.

What are your thoughts?