---
title: Pulmonary Embolism Treatment Algorithm
description: A comprehensive clinical reference on the diagnosis and management of pulmonary embolism.
keywords: [pulmonary embolism, anticoagulation, thrombolysis, CTPA, D-dimer]
category: clinical
---

## Diagnostic Criteria

The diagnosis of pulmonary embolism (PE) is based on a combination of clinical presentation, laboratory tests, and imaging studies. The Wells score is a validated clinical prediction rule that assesses the pretest probability of PE based on factors such as clinical signs and symptoms, risk factors, and alternative diagnoses.

Patients with a Wells score ≥6 (high probability) should proceed directly to computed tomography pulmonary angiography (CTPA) for definitive diagnosis. Those with a Wells score of 2-6 (moderate probability) should undergo D-dimer testing, and if positive, also proceed to CTPA. Patients with a Wells score <2 (low probability) and a negative D-dimer can be ruled out for PE without further imaging.

## Anticoagulation Therapy

The mainstay of treatment for acute PE is anticoagulation. Recommended first-line agents include:

- Unfractionated heparin (UFH): Bolus of 80 U/kg, followed by continuous infusion of 18 U/kg/hr, with aPTT monitoring to maintain a therapeutic range of 60-85 seconds.
- Low-molecular-weight heparin (LMWH): Enoxaparin 1 mg/kg subcutaneously twice daily or Dalteparin 200 IU/kg subcutaneously once daily.
- Direct oral anticoagulants (DOACs): Apixaban 10 mg twice daily for 7 days, followed by 5 mg twice daily; Rivaroxaban 15 mg twice daily with food for 21 days, then 20 mg once daily with food.

Anticoagulation should be continued for a minimum of 3 months, with longer durations considered for patients with unprovoked or recurrent PE, active cancer, or persistent risk factors.

## Thrombolytic Therapy

Systemic thrombolytic therapy is recommended for patients with high-risk or hemodynamically unstable PE, defined as the presence of shock (systolic blood pressure <90 mmHg) or hypotension. Recommended regimens include:

- Alteplase (tPA): 100 mg IV over 2 hours or 0.6 mg/kg IV over 15 minutes (max 50 mg).
- Tenecteplase: Weight-based dosing, ranging from 30 mg IV for patients <60 kg to 50 mg IV for patients ≥90 kg.

Contraindications to thrombolysis include active bleeding, recent surgery or trauma, hemorrhagic stroke within 3 months, and uncontrolled hypertension (systolic BP >180 mmHg or diastolic BP >110 mmHg).

## Mechanical Interventions

For patients with high-risk PE who have contraindications to or fail thrombolytic therapy, mechanical interventions may be considered:

- Catheter-directed thrombolysis: Infusion of a thrombolytic agent (e.g., alteplase 1 mg/hr) directly into the pulmonary artery using a catheter-based system.
- Surgical embolectomy: Removal of the thrombus via open or minimally invasive surgical approaches, reserved for patients with contraindications to both anticoagulation and thrombolysis.
- Percutaneous mechanical thrombectomy: Aspiration or fragmentation of the thrombus using a specialized catheter device.

## Monitoring and Supportive Care

Patients with acute PE should be closely monitored for clinical deterioration, with frequent assessment of vital signs, oxygen saturation, and hemodynamic parameters. Supplemental oxygen should be provided to maintain SpO2 ≥90%.

Laboratory monitoring should include serial D-dimer testing, coagulation studies (aPTT, INR), and cardiac biomarkers (troponin, BNP). The simplified PESI (sPESI) score can be used to risk-stratify patients and guide management decisions.

Patients with high-risk PE or shock should be managed in an intensive care unit setting, with consideration of vasopressor support, mechanical ventilation, and extracorporeal membrane oxygenation (ECMO) as needed.

## Special Populations

Certain patient populations require tailored management approaches for PE:

1. Pregnancy: LMWH is the preferred anticoagulant, with monitoring of anti-Xa levels. Thrombolysis and mechanical interventions should be reserved for life-threatening situations.
2. Cancer-associated thrombosis: LMWH is the recommended initial treatment, with consideration of long-term LMWH or DOAC therapy.
3. Chronic thromboembolic pulmonary hypertension (CTEPH): Evaluation for pulmonary endarterectomy or balloon pulmonary angioplasty should be considered in select cases.

## Conclusion

The management of pulmonary embolism requires a multifaceted approach, incorporating diagnostic algorithms, risk stratification, anticoagulation therapy, and consideration of advanced interventions. Adherence to evidence-based guidelines and close monitoring of patients are essential to optimize outcomes.