Importance of antithrombin therapy during coronary angioplasty.

Angioplasty procedures with balloons, cutters or lasers all may greatly enlarge the arterial lumen, but luminal diameter may decrease because of mural thrombus in 70% to 80%, smooth muscle proliferation, vasoconstriction or recoil. Thrombin binds to arterial wall matrix and fibrin within a thrombus. Heparin dose-dependently decreases platelet and thrombus deposition but does not eliminate these even at high doses. Specific thrombin inhibition started before angioplasty experimentally prevents mural thrombus and limits platelet deposition to a single layer or less. Experimentally, anticoagulant and antifibrin effects occur at lower antithrombin blood levels and lower activated partial thromboplastin times (1.7 times control). Because platelets are so sensitive to thrombin, the higher level of thrombin inhibition required may occur at a specific level (activated partial thromboplastin time greater than or equal to 2 times control); this is not defined in humans. The duration of therapy is not defined in animals or humans. Thrombus and thrombin may be related to cellular proliferation.