Should the patient with a small nonocclusive pulmonary arterial embolus be on heparin?

Should This Patient Be on Heparin?

Yes, this patient with a confirmed subsegmental pulmonary embolus should be started on heparin immediately, despite the small size and nonocclusive nature of the clot. 1, 2

Rationale for Anticoagulation

The presence of any confirmed pulmonary embolism on CT imaging is an indication for therapeutic anticoagulation to prevent:

• Extension of the existing thrombus 1, 3
• Recurrent venous thromboembolism, which carries significant mortality risk 4
• Progression to larger, potentially fatal PE 3

Even subsegmental PE requires treatment because the natural history without anticoagulation includes a 25% risk of recurrent thromboembolism. 4

Immediate Treatment Protocol

Initial Heparin Administration

• Start with an intravenous bolus of 5,000-10,000 units followed by continuous infusion of 400-600 units/kg daily 1
• Alternative dosing: 80 units/kg bolus followed by 18 units/kg/hour continuous infusion 5, 2
• Target aPTT should be 1.5-2.5 times the control value (corresponding to anti-Xa activity of 0.3-0.6 IU/mL) 1, 5

Monitoring Requirements

• Check aPTT approximately every 4 hours initially until therapeutic range achieved, then at appropriate intervals 2
• Monitor platelet counts throughout therapy to detect heparin-induced thrombocytopenia 1, 5
• Perform periodic hematocrit and occult blood in stool testing 2

Choice of Heparin Formulation

Low-molecular-weight heparin (LMWH) is preferred over unfractionated heparin for most patients with PE, as it is at least as effective with more predictable pharmacokinetics. 1, 6

However, unfractionated heparin should be used if:

• Patient has severe renal dysfunction (ESRD on hemodialysis) 5
• Hemodynamic instability is present requiring potential thrombolysis 5
• Need for rapid reversal is anticipated 5

Duration and Transition

• Continue heparin until adequate maintenance anticoagulation with warfarin is achieved (typically 5-7 days with INR 2.0-3.0 for 2 consecutive days) 1, 5, 2
• Warfarin may be started as soon as the diagnosis is confirmed 1
• Total anticoagulation duration should be at least 3 months for unprovoked PE 7

Special Considerations in This Case

Concurrent Infection

The CT shows concerning multifocal infection (possible COVID-19), which creates additional considerations:

• Do not delay anticoagulation due to infection—the PE itself poses immediate mortality risk 1
• Infection may be a provoking factor, but this doesn't change initial treatment 7
• Monitor more closely for bleeding complications given systemic illness 1

No Right Heart Strain

The absence of CT evidence of right heart strain indicates this is not a massive PE, so:

• Thrombolytic therapy is NOT indicated 7
• Standard therapeutic anticoagulation with heparin is appropriate 1, 2
• Hemodynamic monitoring should continue, but aggressive intervention is not needed 5

Contraindications to Assess

Before initiating heparin, verify the patient does NOT have:

• Active bleeding or recent hemorrhage 1
• Recent stroke or intracranial hemorrhage 1
• Current gastrointestinal bleeding 1
• Recent major surgery (within 48-72 hours) 1

If any absolute contraindications exist, consider IVC filter placement instead. 7

Common Pitfalls to Avoid

• Do not withhold anticoagulation because the PE is "small" or subsegmental—size does not determine treatment necessity 4
• Do not use subcutaneous prophylactic-dose heparin for confirmed PE; therapeutic dosing is required 2
• Do not delay treatment waiting for additional testing or specialist consultation when PE is confirmed on imaging 1
• Avoid intramuscular injections during heparin therapy due to hematoma risk 2