What is the management for submassive segmental and subsegmental pulmonary embolism (PE)?

Management of Submassive Segmental and Subsegmental Pulmonary Embolism

Anticoagulation is the first-line treatment for submassive pulmonary embolism, with low molecular weight heparin (LMWH) preferred over unfractionated heparin (UFH) due to equal efficacy and safety. 1

Initial Assessment and Risk Stratification

• Submassive PE is characterized by:

  • Normal systemic blood pressure
  • Evidence of right ventricular dysfunction on imaging
  • Elevated cardiac biomarkers
  • No hemodynamic compromise 1

• Imaging should ideally be completed within 24 hours, with CTPA or echocardiography as the recommended initial imaging modality 1

Treatment Algorithm

Step 1: Initial Anticoagulation

• Begin anticoagulation immediately with one of the following regimens:

1. LMWH (Preferred) 2, 1:

   • Enoxaparin: 1 mg/kg subcutaneously twice daily or 1.5 mg/kg once daily
   • Dalteparin: 200 IU/kg once daily or 100 IU/kg twice daily
   • Tinzaparin: 175 anti-Xa IU/kg once daily

2. Unfractionated Heparin 2:

   • Initial bolus of 80 U/kg followed by continuous IV infusion at 18 U/kg/h
   • Adjust dose to target aPTT corresponding to plasma heparin levels of 0.3-0.7 IU/mL anti-factor Xa activity
   • Target aPTT of 1.5-2.5 times control value 1

3. Fondaparinux 2:

   • 5 mg subcutaneously once daily for patients <50 kg
   • 7.5 mg for patients 50-100 kg
   • 10 mg for patients >100 kg

Step 2: Transition to Long-term Anticoagulation

• After 5-7 days of initial therapy, transition to one of the following:

1. Direct Oral Anticoagulants (DOACs) 3, 4:

   • Apixaban: 10 mg twice daily for 7 days, then 5 mg twice daily
   • Rivaroxaban: 15 mg twice daily with food for 21 days, then 20 mg once daily with food

2. Vitamin K Antagonists (e.g., warfarin) 2:

   • Target INR of 2.0-3.0
   • Overlap with parenteral anticoagulation until INR is therapeutic for at least 24 hours

Step 3: Duration of Anticoagulation

• Standard duration varies based on risk factors 1:
  • 4-6 weeks for temporary risk factors
  • 3 months for first idiopathic event
  • At least 6 months for other cases
  • Consider indefinite therapy for unprovoked PE or ongoing risk factors

Special Considerations

Monitoring

• Monitor for signs of clinical deterioration:
  • Serial echocardiography to assess right ventricular function
  • Vital signs and oxygen requirements
  • Signs of bleeding 1

Patent Foramen Ovale (PFO) Screening

• Consider screening for PFO with echocardiogram with agitated saline bubble study or transcranial Doppler study for risk stratification 2
• If impending paradoxical embolism (thrombus trapped within a PFO) is found, surgical embolectomy may be considered 2

Rescue Interventions for Clinical Deterioration

For patients who deteriorate despite anticoagulation:

1. Catheter Embolectomy and Fragmentation 2, 1:

   • Reasonable for patients with submassive PE who develop clinical evidence of adverse prognosis (new hemodynamic instability, worsening respiratory failure, severe RV dysfunction, or major myocardial necrosis)

2. Surgical Embolectomy 2:

   • May be considered for patients with submassive PE with evidence of adverse prognosis

3. Thrombolytic Therapy 1:

   • May be considered in patients at high risk of hemodynamic deterioration

IVC Filter

• IVC filter should not be used routinely as an adjuvant to anticoagulation in the treatment of acute PE 2
• May be considered for patients with very poor cardiopulmonary reserve 2

Pitfalls and Caveats

1. Misclassification Risk: Submassive PE can rapidly progress to massive PE if not properly monitored. Right ventricular dysfunction is a key indicator of potential deterioration 1

2. Avoid in Submassive PE:

   • Diuretics and vasodilators 1
   • Routine use of IVC filters 2

3. Medication Discontinuation: Premature discontinuation of anticoagulants increases risk of thrombotic events 3, 4

4. Treatment Failure: Low-molecular-weight heparin has been shown to be more effective than unfractionated heparin in preventing recurrent venous thromboembolism in patients with PE 5

By following this structured approach to the management of submassive segmental and subsegmental PE, clinicians can optimize outcomes while minimizing risks of recurrent thromboembolism, bleeding complications, and long-term sequelae.