Effects of local heparin administration on coronary thrombin activity during percutaneous transluminal coronary angioplasty

Simultaneously obtained blood samples from the coronary sinus and systemic arterial circulation were analyzed for antithrombin III (ATIII) activity and fibrinopeptide A (FpA) concentration in nine patients undergoing elective PTCA in order to determine the effects of locally delivered heparin. Samples were obtained at the following designated times: prior to the administration of systemic heparin (period I); 5 min following a loading dose of systemic heparin (period II); 5 min following the final balloon inflation but prior to local delivery (period III); and 5 min following the administration of 4,000 units of unfractionated heparin using a local delivery catheter system (period IV). We found consistent increases in both systemic arterial (P = 0.006) and coronary sinus (P = 0.0002) ATIII activity with systemic heparinization designed to prolong the activated clotting time to 300 sec. However, local delivery of heparin further increased coronary sinus ATIII activity (P = 0.003, period III vs. period IV). FpA concentration decreased in both systemic arterial (P < 0.0001) and coronary sinus (P < 0.0001) samples following systemic heparinization. Moreover, local delivery of heparin further decreased coronary sinus FpA concentration (P = 0.04). Thus, on a background of intense anticoagulation during PTCA, the local delivery of 4,000 units of unfractionated heparin confers incremental antithrombotic activity.