Lit Matters #1: Unfractionated Heparin for PE - effective or antiquated?

Unfractionated heparin produces highly variable anticoagulation in acute pulmonary embolism, with aPTT frequently remaining subtherapeutic through the first 48 hours. For most PE patients, the traditional appeal of heparin as a readily reversible bridge looks weaker when advanced procedures are uncommon.

Unfractionated Heparin in Acute PE

• Variable early anticoagulation: Standard unfractionated heparin dosing for acute PE delivered inconsistent aPTT control, with no 6-hour checkpoint showing even half of patients in the therapeutic range.
• Six-hour aPTT reality: At 6 hours, only 13.9% of bolus-plus-infusion patients were therapeutic, while 51.3% remained subtherapeutic and 34.8% were already supratherapeutic.
• Forty-eight-hour underdosing: By 48 hours, just 28.4% of bolus-plus-infusion patients were therapeutic and 60.6% were still subtherapeutic, arguing against reliable early PE treatment with UFH.
• Therapeutic control over time: Not until 36 hours did half of patients achieve even a single therapeutic aPTT, a useful reality check when heparin is assumed to provide prompt dependable anticoagulation.
• Procedural justification questioned: The usual argument for UFH in PE is easy interruption before thrombolysis or embolectomy, but advanced interventions were rare in this cohort. We get into why that matters in the episode.