What are the types and clinical features of embolism?

Types of Embolism and Their Clinical Features

Embolism is characterized by various types, each with distinct clinical presentations, with thrombotic pulmonary embolism being the most common and potentially fatal form, while non-thrombotic emboli present with diverse manifestations depending on the embolic material and affected vascular bed. 1

Thrombotic Pulmonary Embolism

Classification

• Massive PE: Characterized by shock and/or hypotension (systolic BP <90 mmHg or a drop of 40 mmHg for >15 min) 1
• Submassive PE: Non-massive PE with echocardiographic signs of right ventricular hypokinesis 1
• Non-massive PE: All other cases of PE without hemodynamic compromise or right ventricular dysfunction 1

Clinical Features

• Dyspnea: Most common symptom (80-89%), may be acute and severe in central PE or mild in peripheral PE 2
• Chest pain: Occurs in 40-60% of patients, typically pleuritic due to pleural irritation 2
• Tachycardia: Present in approximately 40% of patients 2
• Syncope/pre-syncope: Associated with hemodynamic instability and right ventricular dysfunction 2
• Hemoptysis: Less common but significant when present 2
• Hypoxemia: Common but not universal (up to 40% of patients have normal oxygen saturation) 2
• Hypocapnia: Often present 2

Non-Thrombotic Pulmonary Embolism

Fat Embolism

• Etiology: Associated with trauma (especially long bone fractures), liposuction, lipid infusions, hepatic necrosis 1
• Clinical Features:
  • Respiratory symptoms, hematological abnormalities, neurological symptoms, cutaneous manifestations
  • Presentation may be fulminating with pulmonary and systemic embolization, right ventricular failure, and cardiovascular collapse
  • More commonly presents gradually with hypoxemia, neurological symptoms, fever, and petechial rash 12-36 hours after injury 1
• Treatment: Non-specific and supportive 1

Venous Air Embolism

• Etiology: Entrainment of air into venous circulation, often iatrogenic (central venous catheter manipulation) 1
• Lethal Volume: 200-300 ml or 3-5 ml/kg injected at 100 ml/s 1
• Clinical Features:
  • Obstruction of right ventricular outflow tract or pulmonary arterioles
  • Cardiovascular dysfunction and failure 1
• Management:
  • Prevention of further air entry
  • Left lateral decubitus position to prevent right ventricular outflow obstruction
  • Aspiration with central venous catheter for large air emboli
  • 100% oxygen administration to decrease bubble size 1

Amniotic Fluid Embolism

• Incidence: 1/8,000-1/80,000 pregnancies 1
• Mortality: High maternal (80%) and fetal (40%) mortality rates 1
• Mechanism: Amniotic fluid forced into uterine veins during labor or when placenta is disrupted 1
• Clinical Features:
  • Seizures in majority of patients
  • Pulmonary edema and acute respiratory distress syndrome
  • Cardiovascular collapse 1
• Management: Supportive care 1

Septic Embolism

• Etiology: Associated with tricuspid valve endocarditis (common in drug addicts), infected indwelling catheters, pacemaker wires, peripheral septic thrombophlebitis 1
• Clinical Features: Fever, cough, hemoptysis 1
• Treatment: Antibiotic therapy, occasionally surgical removal of emboli source 1

Tumor Embolism

• Incidence: Seen in up to 26% of autopsies but rarely diagnosed before death 1
• Common Primary Sites: Prostate, breast, digestive system, liver 1
• Clinical Features: Radiologically mimics pneumonia, tuberculosis, or interstitial lung disease 1
• Treatment: Limited success with chemotherapy, often diagnosed post-mortem 1

Talc Embolism

• Etiology: Intravenous injection of crushed oral medications containing fillers (talc, starch, cellulose) 1
• Mechanism: Filler particles entrapped in pulmonary vasculature causing thrombosis and intravascular granulomata 1

Other Rare Emboli

• Cotton embolism, hydatid embolism, iodinated oil embolism, metallic mercury embolism, cement embolism 1
• Variable clinical presentation depending on embolic material 1

Arterial Embolism

Classification Based on Location

• Acute Limb Ischemia: Characterized by the 5 "Ps": pain, paralysis, paresthesias, pulselessness, and pallor (some add "polar" for cold extremity) 1
• Clinical Categories of Acute Limb Ischemia:
  1. Viable: Not immediately threatened; no sensory loss or muscle weakness; audible arterial and venous Doppler signals 1
  2. Threatened - Salvageable if Promptly Treated: Minimal or no sensory loss; no muscle weakness; often inaudible arterial but audible venous Doppler signals 1
  3. Threatened - Requires Immediate Revascularization: More extensive sensory loss with rest pain; mild to moderate muscle weakness; usually inaudible arterial Doppler signals 1

Common Sites

• Aortoiliac Bifurcation ("saddle embolus"): May produce bilateral lower-limb ischemia, sometimes with reversible paraplegia 1
• Common Femoral Artery: When profunda femoris artery is compromised, more profound ischemia occurs 1
• Superficial Femoral Artery: Common site of thrombosis 1

Management Principles

Anticoagulation

• Cornerstone of PE treatment with mortality rate of 8-15% in first 3 months 2
• Direct Oral Anticoagulants (DOACs) recommended as first-line therapy for most patients 2
• Warfarin is an alternative with target INR 2.0-3.0 for venous thromboembolism 3

Thrombolysis

• Indicated for high-risk PE with hemodynamic instability 2
• Options include rtPA, Streptokinase, and Urokinase 2

Special Considerations

• Pregnancy: LMWH preferred over DOACs or VKAs 2
• Cancer: Extended anticoagulation often required 2
• Renal Impairment: Dose adjustment or alternative anticoagulants needed 2
• Elderly: Higher bleeding risk requiring careful monitoring 2

Complications and Prognosis

• Post-PE Syndrome: Affects up to 47% of patients at 1-year follow-up with persistent dyspnea and exercise limitation 2
• Chronic Thromboembolic Pulmonary Hypertension (CTEPH): Occurs in 2-4% of PE survivors; usually fatal within 2-3 years if untreated 2
• Mortality: Untreated PE has approximately 30% mortality, reduced to 2-8% with adequate treatment 1

Key Diagnostic Considerations

• Clinical presentation of embolism is often non-specific and may mimic other conditions
• Diagnostic approach should be guided by clinical probability assessment and appropriate imaging
• Early recognition and prompt treatment are essential to reduce morbidity and mortality