-Differential antithrombotic therapy in patients with low and high PTCA risk-

Acute coronary occlusion as well as restenosis still represent the major limitations of coronary interventions. Either event seems to be related to thrombus formation. The purpose of this overview is to summarize the current status of the usefulness of conventional and newer antithrombotic drugs regarding the prevention of acute occlusion and restenosis (excluding stents).

For ethical reasons, no placebo-controlled studies were conducted to prove the usefulness of heparin in preventing acute occlusions. The dosage mostly used is 10,000 U, although a relationship between dosage and complication rate has not been documented. A prolonged heparin infusion in patients with low risk and uncomplicated PTCA has no advantages. Restenosis is not influenced by prolonged infusion of heparin or administration of coumadin as well. Low molecular weight heparin is currently under investigation. Hirudin and hirulog have shown promising results with less acute occlusions; however, their therapeutic range must be considered. ANTIAGGREGATION: In controlled studies, ASA significantly reduced acute occlusions during PTCA when given in addition to heparin. Ticlopidin is as effective as ASA, but due to its side effects should only be administered when contraindications to ASA exist. ASA significantly reduced restenosis in only 1 of 4 studies with limited number of patients. Thromboxane inhibitors such as ridogrel or clopidogrel showed promising initial results. Trapidil significantly reduced restenosis in 2 studies; quantitative stenosis analysis, however, was not performed. Inhibition of platelets by glycoprotein (GP) IIb/IIIa receptor antagonists represents an innovative therapeutic concept: numerous controlled trials have documented a significant reduction in cardiac ischemic events and therefore indirectly in restenosis rates. The recombinant monoclonal antibody c7E3 Fab seems to be more effective than the synthetic integrelin. Unfortunately, efficacy appears to be in direct relationship to the risk of bleeding complications. The clinical role of oral GP IIb/IIIa inhibitors has yet to be established. For patients with high risk PTCA, the use of hirudin instead of heparin as well as the addition of GP IIb/IIIa inhibitors should be considered.