What are the diagnostic criteria and treatment options for pulmonary embolism?

Diagnostic Criteria and Treatment Options for Pulmonary Embolism

The diagnosis of pulmonary embolism (PE) should follow a stepwise approach including clinical probability assessment, D-dimer testing, and imaging studies, while treatment should begin with immediate anticoagulation, preferably with direct oral anticoagulants (DOACs) in eligible patients. 1

Diagnostic Criteria

Clinical Probability Assessment

• Use validated clinical prediction rules or clinical judgment to determine the probability of PE 1
• In patients with a probability of PE <15%, the presence of 8 clinical characteristics (age <50 years, heart rate <100/min, oxygen saturation >94%, no recent surgery/trauma, no prior venous thromboembolism, no hemoptysis, no unilateral leg swelling, and no estrogen use) identifies patients at very low risk of PE requiring no further testing 2
• For non-high-risk PE, base the diagnostic strategy on clinical probability assessed either implicitly or using a validated prediction rule 3

Laboratory Testing

• Measure plasma D-dimer in emergency department patients with low or intermediate clinical probability to reduce unnecessary imaging 3, 1
• A normal D-dimer level using either a highly or moderately sensitive assay excludes PE in patients with low clinical probability 3
• Consider using age-adjusted or clinical probability-adjusted D-dimer cutoffs as an alternative to fixed cutoffs 1
• D-dimer measurement is not recommended in high clinical probability patients as a normal result does not safely exclude PE 3

Imaging Studies

• Computed tomography pulmonary angiography (CTPA) is the primary imaging modality for diagnosing PE 3
• Negative MDCT (multi-detector CT) safely excludes PE in patients with low clinical probability 3
• SDCT (single-detector CT) or MDCT showing a segmental or more proximal thrombus confirms PE 3
• For patients with suspected high-risk PE, emergency CT or bedside echocardiography (depending on availability and clinical circumstances) is recommended 3
• Ventilation-perfusion (V/Q) scintigraphy remains a valid option for patients with contraindications to CT, such as allergy to iodine contrast dye or renal failure 3
• Normal perfusion lung scintigraphy excludes PE 3
• High-probability V/Q scan confirms PE in patients with high clinical probability 3
• Lower limb compression ultrasound (CUS) may be considered in selected patients to obviate the need for further imaging if positive for deep vein thrombosis (DVT) 3

Risk Stratification

• After confirming PE in a hemodynamically stable patient, perform further risk assessment involving clinical findings, evaluation of right ventricular function, and laboratory biomarkers 3
• Stratify PE into high-risk (with hemodynamic instability), intermediate-risk, and low-risk categories 1, 4
• Right ventricular evaluation using imaging techniques or laboratory biomarkers should be considered even in patients with low PESI (Pulmonary Embolism Severity Index) or sPESI (simplified PESI) of 0 1
• Acute right ventricular failure with low systemic output is the main cause of death in high-risk PE patients 1

Treatment Options

Anticoagulation

• When initiating oral anticoagulation in a PE patient eligible for a DOAC (apixaban, dabigatran, edoxaban, or rivaroxaban), a DOAC should be preferred over traditional heparin-VKA (vitamin K antagonist) regimens 1, 3
• For patients with suspected high-risk PE, initiate intravenous anticoagulation with unfractionated heparin without delay 1
• If anticoagulation is initiated parenterally in a patient without hemodynamic instability, prefer low-molecular-weight heparin (LMWH) or fondaparinux over unfractionated heparin 1
• Rivaroxaban is FDA-approved for the treatment of PE and reduction in the risk of recurrence 5
• Therapeutic anticoagulation should be administered for at least 3 months to all patients with PE 1

Reperfusion Strategies

• For patients with high-risk PE (with hemodynamic instability), systemic thrombolysis is recommended 4
• In patients with intermediate-high-risk PE, reperfusion is not first-line treatment, but a contingency plan should be ready if the patient's condition deteriorates 3
• For patients showing hemodynamic deterioration despite anticoagulation, rescue thrombolytic therapy is recommended 6
• Surgical embolectomy or catheter-directed treatment should be considered if thrombolysis is contraindicated or fails 6

Duration of Treatment

• Discontinue therapeutic oral anticoagulation after 3 months in patients with a first episode of PE secondary to a transient/reversible major risk factor 1
• Consider extended anticoagulation for patients without an identifiable risk factor for the index PE event 1
• Re-examine the patient after the first 3-6 months of anticoagulation to weigh the benefits vs. risks of continuing treatment 3

Special Situations

Pregnancy

• In pregnant women, consider measuring D-dimer and using clinical prediction rules to rule out PE 1
• Administer fixed therapeutic doses of LMWH, based on early pregnancy weight, in most pregnant women without hemodynamic instability 1
• Do not use DOACs during pregnancy or breastfeeding 1

Hypoxemia Management

• Administer supplemental oxygen in all patients with PE and SaO2 <90%, with escalation of oxygen delivery methods as needed 6
• For patients not responding to conventional oxygen supplementation, consider high-flow oxygen via nasal cannula as the next step 6
• Avoid aggressive fluid challenge as it may worsen right ventricular failure 6

Follow-up

• Perform routine clinical evaluation 3-6 months after acute PE 1
• Implement an integrated care model after acute PE to ensure optimal transition from hospital to outpatient care 1
• Refer symptomatic patients with non-matched perfusion defects on a V/Q scan more than 3 months after acute PE to a specialized center for pulmonary hypertension/chronic thromboembolic pulmonary hypertension (CTEPH) evaluation 1

Common Pitfalls to Avoid

• Delaying anticoagulation while awaiting diagnostic confirmation in patients with high clinical suspicion of PE 3
• Using aggressive fluid challenges in PE patients with right ventricular dysfunction 6
• Overlooking right-to-left shunting through a patent foramen ovale as a cause of refractory hypoxemia 6
• Failing to consider rescue thrombolysis in patients with worsening hypoxemia and hemodynamic deterioration despite anticoagulation 6
• Misdiagnosing single subsegmental PE without confirming with a second opinion, potentially leading to unnecessary anticoagulation 3