What are interesting causes of pulmonary embolism (PE)?

From the Guidelines

Pulmonary embolism can arise from various interesting and uncommon causes, including fat embolism syndrome, amniotic fluid embolism, air embolism, tumor embolism, septic emboli, foreign material emboli, and cement embolism, which require specific management approaches beyond standard anticoagulation. These causes are beyond the typical risk factors such as deep vein thrombosis, and it is essential to consider them in the diagnosis and treatment of pulmonary embolism. According to the American College of Radiology Appropriateness Criteria 1, the diagnosis of pulmonary embolism has been facilitated by technical advancements and multidetector CT pulmonary angiography, which is the major diagnostic modality currently used.

Some of the interesting causes of pulmonary embolism include:

• Fat embolism syndrome following long bone fractures or orthopedic surgery, where fat globules enter the circulation and lodge in pulmonary vessels
• Amniotic fluid embolism, a rare but life-threatening complication during childbirth when amniotic fluid enters the maternal circulation
• Air embolism, which can occur during central line placement, removal, or certain surgical procedures
• Tumor embolism, which happens when cancer cells break off and travel to the lungs, particularly in breast, liver, or gastric cancers
• Septic emboli from endocarditis, which can also cause pulmonary embolism
• Foreign material emboli from intravenous drug use
• Cement embolism, a unique risk during vertebroplasty procedures
• Hydatid cyst rupture, which can release parasitic material that embolizes to the lungs

The management of these unusual causes of pulmonary embolism requires a multidisciplinary approach, including treating the underlying condition, supportive care, and sometimes specialized interventions like hyperbaric oxygen for air embolism or surgical removal for larger foreign material emboli. The American College of Radiology Appropriateness Criteria 1 provides evidence-based guidelines for the diagnosis and treatment of pulmonary embolism, and it is essential to consider these guidelines in the management of patients with pulmonary embolism. Additionally, the use of inferior vena cava (IVC) filters can be considered in select patients with pulmonary embolism, as they can prevent emboli from passing from the lower extremity venous system through the IVC and into the pulmonary arterial circulation 1.

From the FDA Drug Label

In the EINSTEIN DVT and EINSTEIN PE studies, 49% of patients had an idiopathic DVT/PE at baseline Other risk factors included previous episode of DVT/PE (19%), recent surgery or trauma (18%), immobilization (16%), use of estrogen-containing drug (8%), known thrombophilic conditions (6%), or active cancer (5%)

The causes for pulmonary embolism include:

• Idiopathic DVT/PE: 49% of patients
• Previous episode of DVT/PE: 19% of patients
• Recent surgery or trauma: 18% of patients
• Immobilization: 16% of patients
• Use of estrogen-containing drug: 8% of patients
• Known thrombophilic conditions: 6% of patients
• Active cancer: 5% of patients 2

From the Research

Causes of Pulmonary Embolism

• Pulmonary embolism (PE) is typically caused by a thrombus that travels from a vein in a lower limb and occludes blood flow in a pulmonary artery 3
• The incidence of PE is approximately 60 to 120 per 100 000 people per year, with approximately 60 000 to 100 000 patients dying from PE each year in the US 3
• PE can be caused by deep venous thrombosis (DVT), with the two being the most important manifestations of venous thromboembolism (VTE) 4

Risk Factors for Pulmonary Embolism

• Recent surgery or trauma
• Prior venous thromboembolism event
• Hemoptysis
• Unilateral leg swelling
• Estrogen use 3
• Active cancer and pregnancy require long-term use of low-molecular-weight or unfractionated heparin 4
• Obesity, with standard doses of rivaroxaban and apixaban being appropriate for patients up to 150 kg 5

Diagnosis of Pulmonary Embolism

• Assessment of the clinical probability of PE using a structured score or clinical gestalt 3
• D-dimer testing if indicated, with a level of less than 500 ng/mL associated with a posttest probability of PE less than 1.85% 3
• Chest imaging if indicated, with computed tomography pulmonary angiography (CTPA) being the gold standard for diagnosis 6

Treatment of Pulmonary Embolism

• Anticoagulation is the mainstay of VTE treatment, with direct oral anticoagulants such as apixaban, edoxaban, rivaroxaban, or dabigatran being noninferior to heparin combined with a vitamin K antagonist 3
• Systemic thrombolysis is recommended for patients with PE and systolic blood pressure lower than 90 mm Hg, with an associated 1.6% absolute reduction of mortality 3
• Compression therapy is used to prevent postthrombotic syndrome, and acute revascularization procedures are limited to rare special cases 5