A 58-year-old man with a 10-day history of immobilization following a femur fracture presents to the emergency department with acute onset dyspnea, pleuritic chest pain, and tachycardia (HR 112/min). Oxygen saturation is 88% on room air. Clinical suspicion for pulmonary embolism is high. The patient is hemodynamically stable with normal blood pressure. What is the most appropriate next step in management?

Explanation

## Clinical Context This is a hemodynamically stable patient with **high clinical suspicion for PE** (prolonged immobilization, acute dyspnea, pleuritic chest pain, tachycardia, hypoxia with SpO₂ 88%). The Wells score would classify this as high probability (≥6 points). ## Immediate Anticoagulation is the Correct Next Step **High-Yield:** According to current guidelines (ESC 2019, AHA, Harrison's 21e Ch 297), when clinical probability of PE is **high**, anticoagulation should be initiated **immediately — even before imaging confirmation** — provided there are no absolute contraindications. Waiting for CTPA before starting anticoagulation in a high-probability patient risks further thrombus propagation and hemodynamic deterioration. **Key Point:** The distinction is critical: - **Intermediate/low probability** → confirm with CTPA first, then anticoagulate. - **High probability** → start anticoagulation NOW, then confirm with CTPA. ## Why Unfractionated Heparin (UFH)? - **Rapid onset:** UFH achieves therapeutic anticoagulation within minutes of IV bolus. - **Titratable:** Easily adjusted via aPTT monitoring. - **Reversible:** Protamine sulfate can reverse UFH if the patient deteriorates and thrombolysis or surgical embolectomy is needed. - **Preferred in renal impairment and unstable patients** where LMWH pharmacokinetics are less predictable. ## Why Not the Other Options? - **Option A (Warfarin):** Warfarin has a delayed onset (3–5 days) and requires bridging; it is never used as monotherapy in acute PE. - **Option C (CTPA first):** Correct for intermediate-probability patients, but in **high-probability** PE, guidelines mandate anticoagulation before imaging. CTPA should follow, not precede, heparin initiation. - **Option B (Bedside echo):** Useful for risk stratification (massive vs. submassive PE) but not the immediate next step; it does not replace anticoagulation initiation. ## Management Algorithm ``` High clinical suspicion PE (High probability Wells ≥6) ↓ Start UFH immediately (bolus + infusion) ↓ Obtain CTPA to confirm diagnosis ↓ PE confirmed → continue anticoagulation / risk stratify PE not confirmed → investigate alternative diagnosis, stop heparin ``` **Clinical Pearl (Harrison's 21e / ESC PE Guidelines 2019):** "In patients with high clinical probability of PE, anticoagulant treatment should be initiated while awaiting the results of diagnostic tests." UFH is preferred over LMWH in the acute setting due to its rapid reversibility and titratability.