RESUMEN

BACKGROUND: Following percutaneous coronary intervention, combined antiplatelet therapy is necessary. Platelet function testing (PFT) has prognostic value and may be applied in the risk assessment of acute coronary syndrome. In case of combined antiplatelet therapy, PFT may require special laboratory methods, as different antiplatelet agents may influence test results. MATERIALS AND METHODS: Platelet functions were measured in stent thrombosis-segment elevation myocardial infarction patients receiving aspirin, clopidogrel, and tirofiban. The first sampling was obtained immediately after the termination of administration of tirofiban. The second sample was drawn at a randomly assigned time between 1 and 6 h. The third sampling was done after a minimum of 24 h of tirofiban cessation. Adenosine diphosphate (ADP)- and thrombin receptor-activating peptide (TRAP)-induced aggregations were measured. RESULTS: Thirty-seven patients were included. Both TRAP- and ADP-induced aggregation values were significantly lower immediately after tirofiban termination, than after 24 h [TRAP: 26.41 ± 25.00 units (U) vs. 109.86 ± 23.69 U, p < 0.0001; ADP: 17.43 ± 10.10 U vs. 43.92 ± 23.35 U, p ≤ 0.0001]. Elimination half-life of tirofiban and clopidogrel were 1.34 ± 0.49 and 1.269 ± 0.78, respectively. CONCLUSION: ADP-induced residual platelet reactivity is significantly influenced by the presence of concurrent glycoprotein IIb/IIIa inhibitor. In patients receiving combined antiplatelet treatment, ADP-receptor-specific efficiency measurements are valid only after total elimination of GPIIb/IIIa inhibitors.