What is the appropriate anticoagulant therapy for a 70‑year‑old woman with acute pulmonary embolism after recent influenza infection?

Anticoagulation for Acute Pulmonary Embolism in a 70-Year-Old Woman

Start a direct oral anticoagulant (DOAC) such as rivaroxaban 15 mg twice daily for 21 days, then 20 mg once daily, or apixaban with standard dosing, as the preferred first-line treatment for this acute pulmonary embolism. 1

Immediate Treatment Strategy

The European Society of Cardiology (2020) recommends DOACs over traditional heparin-warfarin regimens as first-line therapy for acute PE in hemodynamically stable patients. 1

Why DOACs Are Preferred

• DOACs provide immediate therapeutic anticoagulation without requiring heparin bridging, simplifying management and allowing for potential early discharge. 1, 2
• Lower bleeding rates compared to warfarin make DOACs especially suitable for elderly patients like this 70-year-old woman. 2
• No INR monitoring required, which improves convenience and reduces healthcare visits. 1
• Recent evidence from 2024 shows that patients treated with heparin-to-warfarin strategies had significantly longer hospital stays (2.52 times longer) compared to DOAC-based approaches, with no difference in bleeding or mortality outcomes. 3

Alternative: Traditional Heparin-Based Approach

If DOACs are contraindicated (renal failure with CrCl <30 mL/min, antiphospholipid syndrome, or patient preference for warfarin), use the following protocol:

Initial Heparin Dosing:

• Bolus: 80 IU/kg IV push (approximately 5,000-10,000 units for average adult). 4, 5, 2, 6
• Maintenance infusion: 18 IU/kg/hour (approximately 1,300 IU/hour). 4, 5, 2, 6
• Target aPTT: 1.5-2.5 times control (45-75 seconds). 1, 4, 5, 6

Monitoring Schedule:

• Check aPTT 4-6 hours after initial bolus. 4, 5, 2
• After any dose adjustment, recheck aPTT 6-10 hours later. 4, 5, 2
• Once therapeutic, monitor daily. 1, 4, 5

Transition to Warfarin:

• Start warfarin 5-10 mg daily simultaneously with heparin on day 1. 1, 4, 2
• Continue heparin for minimum 5 days AND until INR ≥2.0 for at least 24 hours before discontinuing heparin. 1, 4, 2, 6
• Target INR: 2.0-3.0. 1, 4, 2

Duration of Anticoagulation

This patient requires at least 3-6 months of full-dose anticoagulation, then reassessment for extended therapy. 1

• If this is her first PE with no identifiable transient risk factor (the influenza infection one month ago is likely not the direct cause), she has an 8% annual recurrence risk and should be considered for indefinite anticoagulation. 1, 2
• After 6 months of full-dose therapy, consider dose reduction to rivaroxaban 10 mg once daily or apixaban 2.5 mg twice daily for extended prophylaxis to reduce bleeding risk while maintaining efficacy. 2
• Reassess bleeding risk every 3-6 months during extended therapy. 2

Risk Stratification and Monitoring

Assess hemodynamic stability immediately to determine if this is high-risk PE requiring thrombolysis consideration:

• Signs of high-risk PE: systolic BP <90 mmHg, shock, distended jugular veins, right-sided S3 gallop. 1, 7
• If hemodynamically unstable, consider thrombolysis with rtPA 100 mg over 2 hours (stop heparin first, resume at maintenance dose after). 1, 4
• For stable patients (which appears to be this case given ER presentation without mention of shock), proceed directly with anticoagulation. 1

Baseline and ongoing monitoring:

• Platelet count at baseline and periodically to screen for heparin-induced thrombocytopenia (if using heparin). 2, 6
• Renal and hepatic function at regular intervals to ensure appropriate DOAC dosing. 2
• Hemoglobin and occult blood testing periodically during anticoagulation. 1, 6

Special Considerations for This Patient

The recent influenza infection (one month ago) is unlikely to be a major transient risk factor justifying short-term anticoagulation only:

• Influenza increases VTE risk primarily during the acute infection period (first 1-2 weeks). 1
• At one month post-influenza, this PE should be considered unprovoked, warranting extended anticoagulation consideration. 1, 2

Age-related considerations for this 70-year-old:

• Advanced age increases both bleeding risk and thrombotic risk. 2, 8
• Actively manage modifiable bleeding risk factors: uncontrolled hypertension, fall risk, concomitant antiplatelet therapy. 2
• Despite age, anticoagulation remains essential—untreated PE carries extremely high mortality. 2, 9

Critical Pitfalls to Avoid

• Do NOT delay anticoagulation while awaiting additional testing or subspecialty consultation—start treatment immediately upon PE diagnosis. 1, 4, 2
• Do NOT use reduced-intensity dosing initially—full therapeutic doses are required for at least the first 6 months. 2
• Do NOT discontinue anticoagulation at 3 months without formal reassessment of recurrence risk versus bleeding risk. 1, 2
• Do NOT use aspirin as primary therapy—it reduces recurrence by only 30-35% compared to 90% with anticoagulation. 2
• If using warfarin, do NOT stop heparin before 5 days regardless of INR, as warfarin's full anticoagulant effect requires depletion of protein C and S. 1, 4, 2, 6