What are the features of pulmonary embolism?

Features of Pulmonary Embolism

Pulmonary embolism (PE) presents with several characteristic clinical features including dyspnea, chest pain, syncope, and hemoptysis, with at least one of these symptoms occurring in 94% of patients with confirmed PE. 1

Clinical Presentations

Common Symptoms

• Dyspnea (shortness of breath) is the most frequent symptom, occurring in approximately 80% of patients with PE, often with sudden onset 2, 1
• Chest pain is present in 39-56% of cases and can be:
  • Pleuritic (sharp pain worsened by breathing) in peripheral PE 2
  • Substernal/angina-like in central PE, potentially representing right ventricular ischemia 2
• Syncope or presyncope occurs in 19-26% of patients and is associated with more severe hemodynamic compromise 2, 1
• Cough affects approximately 20% of patients 2
• Hemoptysis (coughing up blood) is reported in 5-11% of cases 2, 1

Common Signs

• Tachypnea (respiratory rate >20/min) is present in approximately 70% of patients 2
• Tachycardia (heart rate >100/min) occurs in about 26% of patients 2
• Signs of deep vein thrombosis are found in 15% of cases 2
• Fever (>38.5°C) may be present in 7% of patients 2
• Cyanosis is observed in approximately 11% of patients 2

Pathophysiological Presentations

PE can present in three main clinical patterns:

1. High-risk PE (massive PE) - characterized by:

   • Hemodynamic instability with systolic BP <90 mmHg or a drop ≥40 mmHg lasting >15 minutes 2
   • Obstructive shock with signs of end-organ hypoperfusion (altered mental status, cold/clammy skin, oliguria/anuria, increased serum lactate) 2
   • Cardiac arrest requiring cardiopulmonary resuscitation 2

2. Intermediate-risk PE (submassive PE) - characterized by:

   • Hemodynamic stability but with right ventricular dysfunction 2, 3
   • Higher risk of clinical deterioration than low-risk PE 2

3. Low-risk PE - characterized by:

   • Hemodynamic stability without signs of right ventricular dysfunction 2
   • Better prognosis compared to other categories 2

Diagnostic Findings

Radiological Findings

• Chest X-ray abnormalities are common but nonspecific and may include:
  • Atelectasis or infiltrates (49%) 2
  • Pleural effusion (46%) 2
  • Pleural-based opacity/infarction (23%) 2
  • Elevated diaphragm (36%) 2
  • Decreased pulmonary vascularity (36%) 2

Laboratory and Other Findings

• Hypoxemia is frequent, but approximately 40% of patients have normal arterial oxygen saturation 2
• Hypocapnia is often present 2
• Electrocardiographic changes may include:
  • T-wave inversion in leads V1-V4 2
  • QR pattern in V1 2
  • S1Q3T3 pattern 2
  • Right bundle branch block (complete or incomplete) 2
  • Sinus tachycardia (in 40% of patients) 2
  • Atrial arrhythmias, particularly atrial fibrillation 2

Special Considerations

Easily Missed Presentations

• PE may be easily overlooked in:
  • Elderly patients 2
  • Patients with severe cardiorespiratory disease 2
  • Cases where breathlessness is the only symptom ("isolated dyspnea") 2

Pathophysiological Mechanisms

• Right ventricular (RV) failure is a critical determinant of clinical severity and outcome 2
• Ventilation/perfusion mismatch contributes to hypoxemia 2
• Right-to-left shunting through a patent foramen ovale may occur in about one-third of patients, potentially causing severe hypoxemia 2
• Pulmonary infarction can result from small distal emboli, causing hemoptysis, pleuritis, and mild pleural effusion 2

Risk Factors

• Recent immobilization or major surgery 2
• Recent lower limb trauma and/or surgery 2
• Clinical deep vein thrombosis 2
• Previous proven DVT or PE 2
• Pregnancy or post-partum period 2
• Major medical illness 2
• Cancer 2
• Advanced age 2

Clinical Pitfalls

• PE may be asymptomatic or discovered incidentally during diagnostic workup for another disease 2
• In patients with pre-existing heart failure or pulmonary disease, worsening dyspnea may be the only symptom indicating PE 2
• Multiple PEs of different ages are found in 15-60% of cases at necropsy, suggesting that earlier diagnosis could have prevented death 2
• Only 1% of patients have no symptoms before PE is diagnosed 1

Understanding these features is crucial for early recognition and appropriate management of PE, which significantly reduces mortality by up to 75% with proper anticoagulation 2.