Treatment of Subsegmental Pulmonary Embolism
For isolated subsegmental PE without proximal DVT and low recurrence risk, clinical surveillance without anticoagulation is preferred; however, anticoagulation is recommended for high-risk patients or when proximal DVT is present. 1, 2
Mandatory First Step: Exclude Proximal DVT
Before deciding to withhold anticoagulation, you must perform bilateral lower extremity compression ultrasound to exclude proximal deep vein thrombosis 1, 2. This is critical because:
- Isolated subsegmental PE is frequently associated with concurrent DVT 2
- If proximal DVT is detected, full anticoagulation is mandatory regardless of PE location 1, 2
Risk Stratification Determines Treatment Approach
Low-Risk Patients: Clinical Surveillance Preferred
Suggest clinical surveillance over anticoagulation for patients with ALL of the following characteristics 1, 2:
- No active cancer
- No prior history of VTE
- Provoked PE with resolved risk factor
- Good cardiopulmonary reserve
- No proximal DVT on bilateral ultrasound
High-Risk Patients: Anticoagulation Recommended
Suggest anticoagulation over clinical surveillance for patients with ANY of the following 1, 2:
- Active cancer (approximately 20% recurrence rate in first 12 months) 2
- Prior unprovoked VTE
- Persistent risk factors
- Limited cardiopulmonary reserve
- Uncertain diagnosis requiring treatment
Confirm the Diagnosis When Uncertain
Consider additional imaging to confirm the diagnosis when isolated subsegmental filling defects are seen on CT pulmonary angiography, as false-positive findings occur 2. This is particularly important when clinical probability is low.
If Anticoagulation is Chosen
Preferred Agents (Non-Cancer Patients)
Direct oral anticoagulants (DOACs) are preferred over vitamin K antagonists 1:
If DOACs are not used, vitamin K antagonists are preferred over LMWH (Grade 2C) 1.
Preferred Agents (Cancer Patients)
LMWH is preferred for the first 6 months over all other options 1:
Edoxaban or rivaroxaban may be considered as alternatives in patients without gastrointestinal cancer 1.
Duration of Treatment
- Minimum 3 months for all patients receiving anticoagulation 1, 3
- Extended anticoagulation (beyond 6 months) should be considered indefinitely or until cancer is cured in cancer patients 1
If Clinical Surveillance is Chosen
Provide thorough patient education about warning signs requiring immediate return 2:
- New or worsening dyspnea
- Chest pain
- Hemoptysis
- Leg swelling or pain
- Syncope
Special Populations
Incidentally Discovered Subsegmental PE
Treat incidental subsegmental PE the same as symptomatic PE when it involves 1, 4:
- Multiple subsegmental vessels, OR
- Single subsegmental vessel with proven DVT
For truly isolated single subsegmental PE, apply the same risk stratification as symptomatic cases 2.
Cancer Patients
Anticoagulation is strongly recommended regardless of subsegmental location due to high recurrence risk 2. The recurrence rate approaches 20% in the first 12 months without treatment 2.
Critical Pitfalls to Avoid
- Never withhold anticoagulation without first excluding proximal DVT with bilateral ultrasound 1, 2
- Do not assume all subsegmental filling defects represent true PE—consider confirmatory imaging when clinical probability is low 2
- Do not use DOACs in severe renal impairment (CrCl <15 mL/min) or antiphospholipid syndrome 2, 3
- Do not underestimate risk in cancer patients—they require anticoagulation regardless of anatomical location 2
- Avoid inferior vena cava filters as adjunct to anticoagulation—they are not recommended 1
Evidence Quality Note
The recommendations for subsegmental PE management are based on weak recommendations with low-certainty evidence (Grade 2C) 1, reflecting the limited high-quality data in this specific population. However, the approach prioritizes patient safety by requiring DVT exclusion and careful risk stratification before withholding potentially life-saving anticoagulation.