Etiology

• Most common: Deep vein thrombosis
• Causes of nonthrombotic embolism
  • Fat embolism
  • Air embolism
  • Amniotic fluid embolism
  • Bacterial embolism
    • Patients with intravenous drug use are at increased risk of developing tricuspid valve endocarditis, giving rise to septic pulmonary emboli
  • Others: pulmonary tumor embolism, pulmonary cement embolism

Pathophysiology

• The lung is supplied by dual circulation from both the pulmonary arteries and bronchial arteries. This collateral circulation can help protect against lung infarction as a complication of pulmonary embolism (PE).
• Distal PEs in small arteries (�? mm) are more likely to cause infarction as they may occlude areas distal to the pulmonary-bronchial anastomoses.
• When a pulmonary infarction does occur, it is typically hemorrhagic (red) rather than ischemic (white) due to the relatively low density of lung tissue and the dual blood supply.

Clinical features

• Common features of PE
  • Acute onset of symptoms
  • Dyspnea (> 75% of cases)
  • Tachycardia and tachypnea (up to 50% of cases)
  • Sudden pleuritic chest pain (�?20% of cases)
  • Cough and hemoptysis
  • Associated features of DVT: e.g., unilaterally painful leg swelling
• Features of massive PE (e.g., due to a saddle thrombus)
  • Presyncope or syncope
  • Jugular venous distension and Kussmaul sign
    • RV pressure overload
  • Hypotension and obstructive shock
  • Circulatory collapse

Diagnostics

Confirmatory imaging

CT pulmonary angiography (CTPA)

CTPA is the preferred test for the diagnosis of acute PE.

• Findings
  • Direct finding of PE: intraluminal filling defects of pulmonary arteries
  • Pulmonary infarct: opacity with consolidated border; may be accompanied by pleural effusion

Severity assessment

ECG

ECG changes may be due to right ventricular strain and pressure overload.
Most common findings

• T-wave inversions or flattening
• Sinus tachycardia
• Normal ECG
• S₁Q₃T₃ pattern (neither sensitive nor specific)
  Predictors of adverse outcomes: See “High-risk ECG findings in PE.�?Other ECG findings in PE: sinus bradycardia (< 60/min); uncommon)

Treatment

Reperfusion therapy

• Indications
  • Massive PE (hemodynamic instability and/or right heart failure) with a low bleeding risk
• Recombinant tissue plasminogen activator (tPA), e.g., alteplase (preferred)
  • Endothelial-derived TPA is limited primarily to the bronchial circulation, and spontaneous recanalization of the pulmonary artery is a slow process.