## Why Systemic thrombolysis with alteplase IV is right A thrombus straddling the **pulmonary arterial bifurcation (D)** and extending into both main pulmonary arteries constitutes a **saddle PE** — a massive, high-risk pulmonary embolism. The clinical presentation of shock (BP 85/50), syncope, and RV strain (RV/LV ratio 1.2 > 0.9) confirms hemodynamic instability. According to Harrison 21e Ch 279, massive PE with shock or sustained hypotension requires **immediate systemic thrombolysis with alteplase IV** unless contraindicated. CTPA is the gold standard imaging (sensitivity > 95%) for visualizing filling defects at the bifurcation level and assessing RV strain, which guides risk stratification and treatment escalation. ## Why each distractor is wrong - **Anticoagulation with apixaban and close monitoring**: This is appropriate for intermediate-high-risk PE (RV dysfunction + biomarker elevation without shock). The patient has hemodynamic instability (shock, syncope), which mandates thrombolysis, not anticoagulation alone. - **Anticoagulation with warfarin and observation**: Warfarin is no longer preferred for acute PE management; DOACs are preferred. More critically, this patient has massive PE with shock and requires thrombolysis, not observation. - **Catheter-directed thrombolysis with heparin bridge**: While catheter-directed thrombolysis may be considered in intermediate-high-risk PE or when systemic thrombolysis is contraindicated, it is not first-line for hemodynamically unstable massive PE. Systemic thrombolysis is the immediate standard of care. **High-Yield:** Saddle PE at the bifurcation with shock = systemic thrombolysis; intermediate-high PE with RV strain but no shock = anticoagulation + monitoring. [cite: Harrison 21e Ch 279]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.