Prevalence of and Eligibility for Surveillance Without Anticoagulation Among Adults With Lower-Risk Acute Subsegmental Pulmonary Embolism

Key Points Question How prevalent is structured surveillance without anticoagulation for subsegmental pulmonary embolism in community practice, and what proportion of patients are surveillance eligible using modified American College of Chest Physicians (CHEST) criteria? Findings In this cohort study of 666 outpatients examined over 5 years after publication of the 2016 CHEST guideline, only 1 patient (<1%) with subsegmental pulmonary embolism underwent surveillance without anticoagulation in a community setting with excellent follow-up access. Using modified CHEST criteria, 35 patients (5%) with subsegmental pulmonary embolism were surveillance eligible. Meaning These findings suggest that only a small proportion of patients with subsegmental pulmonary embolism may be surveillance eligible, and structured surveillance is rarely used despite the CHEST guideline. This cohort study examines the prevalence of and eligibility for structured surveillance of adult outpatients with acute subsegmental pulmonary embolism, according to modified American College of Chest Physicians criteria. Importance Approximately 8% of acute pulmonary emboli are confined to the subsegmental arteries. The 2016 and 2021 American College of Chest Physicians (CHEST) guidelines and expert panel reports suggest the use of structured surveillance without anticoagulation for select ambulatory patients with subsegmental pulmonary embolism who do not have active cancer, deep vein thrombosis, impaired cardiopulmonary reserve, marked symptoms, or increased risk of recurrent venous thromboembolism; however, guideline uptake in community practice is unknown, as is the proportion of outpatients eligible for surveillance. Objective To describe the prevalence of surveillance among outpatients with acute subsegmental pulmonary embolism and to estimate the proportion of patients eligible for structured surveillance using modified CHEST criteria. Design, Setting, and Participants This retrospective cohort study was conducted across 21 US community hospitals in the Kaiser Permanente Northern California integrated health system from January 1, 2017, to December 31, 2021. Adult outpatients with acute subsegmental pulmonary embolism were included. Patients with the following higher-risk characteristics were excluded: codiagnoses requiring hospitalization, non-low-risk vital signs (ie, systolic blood pressure <90 mm Hg, pulse >= 110 bpm, or peripheral cutaneous pulse oximetry <= 92%), prediagnosis anticoagulant use, or hospice care. Data analysis was performed from November 2022 to February 2023. Main Outcomes and Measures The main outcomes were the (1) prevalence of surveillance and (2) eligibility for surveillance using 2 sets of criteria: the CHEST criteria modified by excluding patients with higher-risk characteristics or right ventricular dysfunction and a stricter set of criteria requiring age younger than 65 years and no more than 1 embolus. The prevalence of structured surveillance was calculated and the proportion of patients eligible for surveillance was estimated. Results Of the 666 outpatients with acute subsegmental pulmonary embolism included in this study, 229 with lower-risk characteristics were examined. Their median age was 58 (IQR, 42-68) years; more than half were men (120 [52.4%]) and self-identified as non-Hispanic White (128 [55.9%]). Six patients (2.6%) were initially not treated with anticoagulants. Among the lower-risk cohort, only 1 patient (0.4% [95% CI, 0.01%-2.4%]) underwent structured surveillance, without 90-day sequelae. Thirty-five patients (15.3% of the lower-risk group and 5.3% of the full cohort) were surveillance eligible using modified CHEST criteria. Fifteen patients (6.6% of the lower-risk group and 2.3% of the full cohort) were surveillance eligible using stricter criteria. Conclusions and Relevance In this cohort study of lower-risk outpatients with subsegmental pulmonary embolism, few were eligible for structured surveillance, and only a small proportion of eligible patients underwent surveillance despite the CHEST guideline. If forthcoming trials find surveillance safe and effective, substantial uptake into clinical practice may require more than passive diffusion.