## Saddle Embolus: Definition and Hemodynamic Significance **Key Point:** A saddle embolus is a thrombus that straddles the bifurcation of the main pulmonary artery, extending into both the right and left main pulmonary arteries. It is a hallmark of massive PE and carries very high mortality risk. ### Anatomical and Clinical Features **High-Yield:** Saddle embolus characteristics: - Located at the pulmonary artery bifurcation - Extends symmetrically into both right and left main pulmonary arteries - Represents massive PE (>50% pulmonary vascular obstruction) - Associated with acute right ventricular failure and cardiogenic shock - Mortality rate: 30–50% if untreated; 10–15% with aggressive treatment (thrombolysis or embolectomy) ### Hemodynamic Consequences | Parameter | Effect | Mechanism | |-----------|--------|----------| | RV afterload | ↑↑ Marked increase | Massive vascular obstruction | | RV pressure | ↑↑ Acute elevation | Acute cor pulmonale | | Cardiac output | ↓↓ Severe reduction | RV failure and shock | | Systemic BP | ↓ Hypotension | Cardiogenic shock | | Mortality | Very high | Acute hemodynamic collapse | **Clinical Pearl:** Saddle embolus is a *radiological emergency*. Patients typically present with: - Acute hemodynamic instability (shock, syncope) - Severe dyspnea - Elevated troponin and BNP - Requires immediate thrombolysis or embolectomy **Mnemonic:** **SADDLE** = **S**traddling **A**rtery **D**ivision **D**ual **L**umen **E**mbolus **Warning:** Do not confuse saddle embolus with: - Subsegmental PE (low mortality, often managed conservatively) - Chronic thromboembolic disease (gradual onset, organized thrombus) - Paradoxical embolism (venous thrombus crossing PFO into systemic circulation) 
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