A 58-year-old man with a 2-week history of left leg swelling and pain presents to the emergency department with acute-onset dyspnea, chest pain, and syncope. His blood pressure is 78/52 mmHg despite fluid resuscitation, and he is in acute respiratory distress. A CT pulmonary angiogram shows a large thrombus straddling the bifurcation of the main pulmonary artery, as marked **A** in the diagram. Which of the following best describes the hemodynamic classification and immediate management priority for this presentation?

Explanation

## Why "Massive/high-risk PE with hemodynamic instability requiring urgent systemic thrombolysis or catheter-directed intervention" is right A saddle thromboembolus at the bifurcation of the main pulmonary artery (marked **A**) is the pathologic hallmark of massive pulmonary embolism. The clinical presentation of sustained hypotension (SBP < 90 mmHg) in this patient defines hemodynamic instability, which is the KEY distinguishing feature of high-risk/massive PE. According to Harrison 21e Ch 279, saddle PE arising from lower extremity DVT (95% of PE sources) presents with hemodynamic instability and requires emergency intervention—either systemic thrombolysis, catheter-directed thrombolysis, or surgical embolectomy—plus ICU admission. The syncope and shock state in this case mandate immediate multidisciplinary consultation (vascular surgery, interventional radiology, cardiothoracic surgery) and consideration of ECMO if cardiac arrest ensues. ## Why each distractor is wrong - **Submassive/intermediate-risk PE with RV strain requiring anticoagulation and close monitoring without thrombolysis**: Submassive PE is defined by hemodynamic STABILITY but with RV strain on imaging or elevated cardiac biomarkers. This patient is hemodynamically unstable (SBP 78/52), which excludes the intermediate-risk category. Anticoagulation alone is insufficient for massive PE. - **Low-risk PE with stable hemodynamics suitable for outpatient anticoagulation alone**: Low-risk PE requires hemodynamic stability, absence of RV strain, and normal cardiac biomarkers. This patient has profound hypotension and syncope, clearly excluding low-risk classification. Outpatient management would be fatal. - **Chronic thromboembolic pulmonary hypertension requiring pulmonary endarterectomy**: CTEPH is a long-term sequela developing in ~4% of acute PE survivors who have unresolved thrombus. It presents with chronic dyspnea and pulmonary hypertension, not acute hemodynamic collapse. Endarterectomy is a definitive therapy for chronic disease, not acute massive PE. **High-Yield:** Saddle PE = large thrombus at PA bifurcation = MASSIVE PE = hemodynamic instability (SBP < 90 or vasopressor need or cardiac arrest) = EMERGENCY thrombolysis/intervention, NOT anticoagulation alone. [cite: Harrison 21e Ch 279; SME batch 11–14 PE classification and management]