Pulmonary embolism (PE), the great imposter, should be considered in virtually any ED visit related to weakness, shortness of breath, dizziness/syncope, pain, extremity discomfort, or nonspecific malaise or functional deterioration.

Key History

Key Physical Exam

Risk Factors for PE

Differential Diagnosis

Diagnostic Testing

The diagnostic testing for pulmonary embolism (PE) involves a combination of clinical assessment, laboratory tests, and imaging studies to confirm or exclude the diagnosis efficiently and accurately.

Clinical Prediction Rules:

• Wells Score and Geneva Score are commonly used to stratify patients into low, intermediate or high pretest probability categories for PE.

Laboratory Tests:

• D-Dimer Assay: A highly sensitive but non-specific test. A normal D-dimer level can effectively rule out PE in patients with low or intermediate pretest probability.

Imaging Studies:

• Computed Tomography Pulmonary Angiography (CTPA): The first-line imaging modality for diagnosing PE due to its high sensitivity and specificity. It directly visualizes thromboemboli in the pulmonary arteries and can also suggest alternative diagnoses.
• Ventilation-Perfusion (V/Q) Scan: An alternative to CTPA, particularly useful in patients with contraindications to contrast media. A normal V/Q scan can safely exclude PE, but indeterminate results often necessitate further testing.
• Compression Ultrasonography (CUS): Used to detect deep vein thrombosis (DVT) in the lower extremities, which is often associated with PE. A positive CUS can support the diagnosis of PE, especially in patients with contraindications to CTPA.

Pulmonary Angiography:

• Considered the gold standard but is rarely used due to its invasiveness, high cost, and limited availability. It is reserved for cases where non-invasive tests are inconclusive and a definitive diagnosis is critical.

Algorithmic Approach:

• The American College of Physicians recommends using clinical prediction rules and D-dimer testing to guide the need for imaging studies. For patients with high pretest probability, imaging studies should be performed directly without D-dimer testing.

Wells Criteria & PERC Rule

Clinical Risk and Safety Pearls

• The literature now supports a risk stratification strategy as described above.
• Immediate full anticoagulation for patients suspected of having DVT and/or PE is suggested.
• Diagnostic testing should not delay empirical anticoagulant therapy.
• D-dimer is not helpful if the patient has an active malignancy or has had recent surgery.
• Up to 60% of patients with a PE have a normal ultrasound study of the lower extremity.
• The onset of SOB typically occurs a few days before the patient presents to the ED with complaints.
• Less than half of patients present with sudden onset of SOB or chest pain.

Treatment

The treatment options for pulmonary embolism (PE) are stratified based on the patient's hemodynamic stability and risk profile.

Anticoagulation:

• Initial Therapy: For most patients, initial anticoagulation is critical. Options include low-molecular-weight heparin (LMWH), unfractionated heparin (UFH), or fondaparinux. These agents are typically administered subcutaneously or intravenously.
• Direct Oral Anticoagulants (DOACs): For hemodynamically stable patients, DOACs such as rivaroxaban, apixaban, edoxaban, and dabigatran are preferred due to their ease of use and lower bleeding risk compared to vitamin K antagonists (VKAs).

Thrombolysis:

• Systemic Thrombolysis: Indicated for patients with massive PE (hemodynamic instability or shock). Agents like alteplase are used to rapidly dissolve the thrombus.
• Catheter-Directed Thrombolysis: For patients with submassive PE (right ventricular dysfunction without shock) or those with contraindications to systemic thrombolysis, catheter-directed approaches can be considered.

Surgical and Interventional Therapies:

• Surgical Embolectomy: Reserved for patients with massive PE who have contraindications to thrombolysis or in whom thrombolysis has failed.
• Catheter-Based Embolectomy: Techniques such as suction thrombectomy and mechanical fragmentation are emerging options for patients with high-risk PE.

Inferior Vena Cava (IVC) Filters:

• Used in patients with contraindications to anticoagulation or recurrent PE despite adequate anticoagulation.

Long-Term Anticoagulation:

• Following initial treatment, long-term anticoagulation is typically continued for at least 3-6 months. The choice between DOACs and VKAs depends on patient-specific factors, including the presence of malignancy or renal impairment.
• The American Heart Association recommends prompt anticoagulation for all patients with confirmed PE and no contraindications, with thrombolysis reserved for those with hemodynamic instability.