How is pulmonary embolism (PE) treated in patients resistant to heparin?

Updated: Jun 06, 2019
  • Author: Daniel R Ouellette, MD, FCCP; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Answer

Few patients with venous thromboembolism require large doses of heparin for achieving an optimal activated partial thromboplastin time (aPTT). Those patients who do require them have increased plasma concentrations of factor VIII and heparin-binding proteins. Increased factor VIII concentration causes dissociation between aPTT and plasma heparin values. The aPTT is suboptimal, but patients have adequate heparin levels upon protamine titration. This commonly occurs in patients with a concomitant inflammatory disease.

Monitoring the antifactor Xa assay results in this situation is safe and effective and results in less escalation of the heparin dose when compared with monitoring with aPTT. Whenever a therapeutic level of aPTT cannot be achieved with large doses of UFH, either determination of plasma heparin concentration or therapy with LMWH should be instituted.


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