Types of emboli

1. Definition

• Embolus = detached intravascular solid/liquid/gas mass carried by blood to a distant site → occlusion → ischemic necrosis (infarct).
• 99% are thromboemboli (displaced thrombi). Pulmonary or systemic circulation.

2. Pulmonary Thromboembolism

• Origin: ~95% from deep leg veins (above knee) → right heart → pulmonary vasculature.
• Types: saddle embolus (at bifurcation), total (both lungs → sudden death), sub-total (one lung), partial (small vessels), paradoxical (vein→artery via shunt).
• Consequences: most clinically silent (small); ≥60% obstruction → sudden death/RV failure; medium vessels → hemorrhage (no infarct due to dual blood supply, unless left HF); small end-artery → infarct.

3. Systemic Thromboembolism

• Arterial circulation; 80% from the heart (LV mural thrombus post-MI, atrial fibrillation); also aortic aneurysm, ulcerated plaque, valvular vegetation.
• Travels to extremities, brain (also kidney, spleen, intestine) → infarcts.

4. Non-Thrombotic Emboli

Type	Source	Key features
Fat	Long-bone fracture, soft-tissue trauma	Mechanical occlusion + FFA endothelial toxicity → respiratory distress, neuro symptoms, anemia/thrombocytopenia
Air / gas	Obstetric/chest procedures, diving	Decompression sickness — N₂ bubbles (“bends”); treat with recompression
Amniotic fluid	Labor (placental tear / uterine vein rupture)	Sudden dyspnea, shock, → DIC
Tumor cell	Neoplastic fragments	Ischemia + metastatic seeding

💡 High-yield: 99% emboli = thromboemboli. PE usually from DVT (above knee); saddle embolus → sudden death. Lung has dual supply → infarct only if left HF or small end-artery. Non-thrombotic: fat (long-bone #), air (decompression), amniotic fluid (→DIC), tumor.