Subsegmental Pulmonary Embolism Linked to Increased Rate of VTE

Marc Carrier, MD

Although the incidence rates of pulmonary embolism have been increasing, conversely, the case-fatality rate has decreased, which may suggest lower severity of illness.

As the clinical importance of patients with pulmonary embolism isolated to the subsegmental vessels is unknown, a team of investigators sought to determine the rate of recurrent venous thromboembolism (VTE) in patients with subsegmental pulmonary embolism being managed without anticoagulation.

Led by Marc Carrier, MD, MSc, The Ottawa Hospital, they observed patients with subsegmental pulmonary embolism without proximal deep venous thrombosis had a higher rate of recurrent VTE than what was expected.

The design of the study was a multi-center, prospective cohort study, which occurred at 18 sites between February 2011 - February 2021. The inclusion of patients were those with isolated subsegmental pulmonary embolism.

Investigators noted that at diagnosis, patients underwent bilateral lower-extremity venous ultrasonography, which would be repeated after 1 week if the results were negative. However, patients without deep venous thrombosis did not receive anticoagulant therapy.

They considered the primary outcome of the study to be a recurrent VTE during a 90-day follow-up period.

During the study period, recruitment was stopped prematurely due to the predefined stopping rule being met after 292 patients were enrolled in the study, out of the projected 300 patients.

Then, 266 patients were included in the primary analysis. Data show the primary outcome occurred in 8 patients, at a cumulative incidence of 3.1% (95% CI, 1.6% - 6.1%) throughout the 90-day follow-up.

Additionally, the incidence of recurrent VTE was shown to be 2.1% (95% CI, 0.8% - 5.5%) in patients with single isolated subsegmental pulmonary embolism.  Data show the incidence rate was 5.7% (95% CI, 2.2% - 14.4%) over the 90-day follow-up in patients with multiple isolated subsegmental pulmonary embolism.

They observed no patients had a fatal recurrent pulmonary embolism.

Carrier and colleagues noted limitations of the study included a restriction on patients with low-risk subsegmental pulmonary embolism.

“Overall, patients with subsegmental pulmonary embolism who did not have proximal deep venous thrombosis had a higher-than-expected rate of recurrent venous thromboembolism,” they wrote.

The study, “Risk for Recurrent Venous Thromboembolism in Patients With Subsegmental Pulmonary Embolism Managed Without Anticoagulation,” was published online in Annals of Internal Medicine.