Heparin: Physiology, Pharmacology, and Clinical Application

Heparin is stored endogenously within the secretory granules of basophils and mast cells, and is only released into the vasculature at sites of injury. At these sites, it helps maintain proper blood flow by balancing the active anticoagulant and procoagulant processes. Pharmaceutical-grade heparin is derived from animal tissue, but one form is made synthetically. Heparin is commonly used in the management of coronary artery disease, deep vein thrombosis, pulmonary embolism, and atrial fibrillation, and in the prevention of thrombosis during cardiopulmonary bypass and extracorporeal membrane oxygenation. Heparin treatment is a key component in elective percutaneous coronary intervention (PCI). It plays an important role in minimizing the risk of thrombotic events during PCI and is one of the most popular anticoagulants used. However, some studies show that higher heparin doses are associated with more frequent bleeding complications, which can increase morbidity and mortality. The optimal heparin dosing regimens are still debated, as well as their efficacy in PCI compared with that of other drugs such as bivalirudin. This review examines the physiology, pharmacology, therapeutic applications, dosing regimens, and efficacy of heparin in the setting of PCI. In addition, included is a review of data on addition of glycoprotein IIb/IIIa inhibitors to heparin and comparison of heparin monotherapy to bivalirudin in PCI.