Pharmacology of Venous Thromboembolism

The ability to clot is crucial to human survival. Without clot formation, minor injuries would result in significant blood loss and eventual death. Likewise, the ability to regulate blood clot formation is essential to human survival as unregulated clot formation will lead to vessel occlusion and possible death. The balance of clot formation and degradation must be continually maintained. We can thank Rudolf Virchow and Virchow’s Triad for recognizing the risk factors that disrupt this balance and tip the scales toward venous thromboembolism (VTE):1

  1. Stasis
  2. Hypercoagulability
  3. Endothelial damage

Additional information regarding risk factors can be seen at this Life in the Fast Lane evidence-based review.

VTE has a wide range of severity from an incidental finding all the way to a limb-threatening and even life-ending occlusion. Blood clots can form anywhere, and like real estate, location is important. On the low end of the severity spectrum is the isolated distal deep vein thrombosis (DVT) with low risk of extension that may be managed under surveillance without anticoagulant therapy.2 Similarly, the finding of a subsegmental pulmonary embolism (PE) with no proximal DVT may also be managed with surveillance.2 On the high end of the severity spectrum there is an estimate that as many as 11% of patients with acute PE die within one hour.1 With an incidence in the millions worldwide, diagnosing and treating VTE is a daily occurrence in the emergency department (ED).

Emergency providers must focus on the recognition and immediate treatment of potentially life-threatening disease states. To aid in the diagnosis of PE, decision tools such as the Pulmonary Embolism Clinical Prediction Rules (PERC), the Wells’ score, and the simplified Geneva score are available for diagnostic workup and can be reviewed in the ALiEM Card. The initial and emergent pharmacologic management of VTE in the ED will be the focus of this module.

Learning Objectives

  • Distinguish mechanistic differences between anticoagulation and thrombolysis
  • Explain treatment options for DVT and PE
  • Optimize treatment selection based upon patient and medication specific variables
  • Design anticoagulation regimens for special populations

Page References

1.
Dalen J. Pulmonary embolism: what have we learned since Virchow? Natural history, pathophysiology, and diagnosis. Chest. 2002;122(4):1440-1456. [PubMed]
2.
Kearon C, Akl E, Ornelas J, et al. Antithrombotic Therapy for VTE Disease: CHEST Guideline and Expert Panel Report. Chest. 2016;149(2):315-352. [PubMed]