What is the most appropriate next step in care for a patient with a large, segmental pulmonary embolism, hypotension, and tachycardia, with normal troponin and natriuretic peptide levels?

Heparin IV Bolus and Drip

This patient requires immediate anticoagulation with IV heparin bolus and drip, not thrombolysis, because she does not meet criteria for massive pulmonary embolism despite initial hypotension that responded to fluid resuscitation. 1, 2

Why This Patient Does NOT Have Massive PE

This case represents a critical diagnostic distinction. While the patient presented with hypotension (80/50 mmHg), her blood pressure improved to 85/60 mmHg after just 1 liter of IV fluids and was sustained for at least 1 hour. 1

Massive PE requires sustained hypotension:

• Systolic blood pressure <90 mmHg for at least 15 minutes or requiring inotropic support 1
• The European Society of Cardiology similarly defines massive PE as shock/hypotension with SBP <90 mmHg or pressure drop of 40 mmHg for >15 minutes, provided these are not caused by new-onset arrhythmia, hypovolemia, or sepsis 3

This patient's hypotension was transient and fluid-responsive, which excludes the diagnosis of massive PE. Her presentation is more consistent with hypovolemia or initial presentation hypotension that resolved with supportive care. 3

Additional Evidence Against Thrombolysis

Normal cardiac biomarkers argue strongly against high-risk PE:

• Her troponin and natriuretic peptide levels are normal, indicating absence of significant right ventricular strain 3, 4
• The American Heart Association algorithm for fibrinolysis specifically requires evidence of moderate-to-severe RV strain, including RV dysfunction on echo OR clearly elevated biomarker values (troponin above borderline, BNP >100 pg/mL or pro-BNP >900 pg/mL) 3
• This patient has neither hemodynamic instability (after fluid resuscitation) nor biomarker evidence of RV dysfunction 3

Correct Management: Anticoagulation

Immediate anticoagulation with unfractionated heparin is the appropriate treatment:

• Start anticoagulation immediately in confirmed PE unless actively bleeding or absolute contraindications exist 2
• For this patient with initial hemodynamic instability (even though resolved), unfractionated heparin IV is preferred over LMWH because it allows rapid reversal if needed and provides more predictable pharmacokinetics in the acute setting 2
• The standard regimen is an 80 units/kg IV bolus followed by 18 units/kg/hour continuous infusion, adjusted to maintain aPTT 1.5-2.5 times control 5

Why NOT the Other Options

Alteplase IV would be inappropriate and potentially harmful:

• Thrombolysis carries 15% major bleeding risk and should be reserved for truly massive PE with sustained hypotension or submassive PE with evidence of RV dysfunction 3, 6
• This patient meets neither criterion after fluid resuscitation 3, 1

Enoxaparin IV is not indicated:

• Enoxaparin is given subcutaneously, not IV (except for a 30 mg IV bolus in STEMI protocols) 5
• While LMWH is preferred in stable PE, this patient's initial instability makes unfractionated heparin more appropriate for immediate reversibility 2

Surgical embolectomy is reserved for:

• Patients with massive PE who have absolute contraindications to thrombolysis 3
• Patients who fail thrombolytic therapy and remain in shock 3
• This patient requires neither intervention 3

Critical Clinical Pitfall

The key error to avoid is misclassifying transient, fluid-responsive hypotension as massive PE. The 15-minute threshold for sustained hypotension exists precisely to distinguish true cardiogenic shock from other reversible causes. 1 Administering thrombolysis to this patient would expose her to unnecessary 15% bleeding risk without mortality benefit. 6