A 58-year-old man with a 3-day history of left leg swelling and pain presents to the emergency department with acute-onset dyspnea, severe chest pain, and hypotension (SBP 78 mmHg). A CT pulmonary angiogram shows a large thrombus straddling the bifurcation of the main pulmonary artery and extending into both right and left main pulmonary arteries, as marked **A** in the diagram. The patient is in cardiogenic shock with altered mental status. Which of the following is the most appropriate immediate management?

Explanation

## Why Systemic thrombolysis with alteplase 100 mg IV over 2 hours is right A saddle pulmonary embolus straddling the bifurcation of the main pulmonary artery (marked **A**) is a MASSIVE (HIGH-RISK) PE, defined by sustained hypotension (SBP < 90 mmHg for > 15 minutes) and/or cardiogenic shock. This patient meets criteria: SBP 78 mmHg with altered mental status and hemodynamic instability. According to current ESC/AHA guidelines and Harrison 21e Ch 279, the standard of care for massive PE is SYSTEMIC THROMBOLYSIS with alteplase 100 mg IV over 2 hours (or faster regimens in severe shock). Concurrent management includes cautious IV fluid resuscitation (small boluses 250–500 mL with reassessment to avoid RV failure) and vasopressor support with norepinephrine, which is preferred over saline alone in shock states. The large thrombus burden at the bifurcation (source typically from ileofemoral DVT in the lower extremity) requires urgent clot dissolution to restore pulmonary perfusion and prevent sudden death. ## Why each distractor is wrong - **Anticoagulation with unfractionated heparin alone**: While UFH is appropriate for unstable patients, anticoagulation ALONE is insufficient for massive PE with hemodynamic instability. Anticoagulation prevents clot propagation but does not dissolve existing thrombus; thrombolysis is required to restore perfusion urgently. - **Insertion of an inferior vena cava filter**: IVC filters are reserved for contraindications to anticoagulation or recurrent PE despite adequate anticoagulation—neither applies here. Filters do not treat the acute massive PE and delay definitive thrombolysis, increasing mortality risk in this high-risk scenario. - **Observation with oxygen and deferred thrombolysis**: Watchful waiting is appropriate only for LOW-RISK PE (hemodynamically stable, no RV strain, no biomarker elevation). A saddle embolus with shock and altered mental status is a medical emergency requiring immediate thrombolysis; delay is life-threatening. **High-Yield:** Saddle PE = massive PE = sustained hypotension or shock = systemic thrombolysis (alteplase 100 mg IV/2 hr) ± vasopressor + cautious fluids; anticoagulation alone is inadequate. [cite: Robbins 10e Ch 4; Harrison 21e Ch 279]