BACKGROUND AND OBJECTIVES: The therapeutic efficacy of combined platelet glycoprotein IIb/IIIa receptor blocker with low molecular weight heparin (LMWH) is unknown for patients with acute myocardial infarction (AMI) and who underwent percutaneous coronary intervention (PCI). SUBJECTS AND METHODS: A total of 140 patients with AMI and who underwent high-risk PCI was divided into two groups: UFH (group I: 70 patients, 58.7+/-10.5 years of age), and dalteparin (group II: 70 patients, 59.6+/-9.8 years of age). The major adverse cardiac events (MACE) during hospitalization and during the 4 years after PCI were evaluated. RESULTS: The baseline clinical characteristics and angiographic characteristics were not different between the two groups. There were 62.9% totally occluded lesions with thrombus in both groups. Procedural success was achieved for 91.4% of the group I patients and for 90.0% of the group II patients. Any bleeding and hemorrhagic events were not different between the two groups. No significant intracranial bleeding was observed in both groups. The number of in-hospital MACEs was 7 (10.0%) in group I and 4 (5.7%) in group II. Four-year clinical follow-up was performed for 97% of the patients. As a result of the MACEs during the 4 years after PCI, death occurred in 6 (8.6%) patients in group I and in 7 (10.0%) patients in group II. Myocardial infarction occurred in 4 (5.7%) and 4 (5.7%) patients, respectively, target vessel revascularizations were done in 23 (32.9%) and 16 (22.9%) patients, respectively, and coronary artery bypass surgery was done in 3 (4.3%) and 1 (1.4%) patients, respectively. Overall, MACEs occurred in 33 (47.1%) patients of group I and in 26 (35.1%) patients of group II during the 4-year clinical follow-up (p=0.23). CONCLUSION: The long-term clinical outcome of dalteparin combined with abciximab is comparable with that of UFH plus abciximab for the high risk patients with AMI who receive PCI.