Summary
It was the aim of this study to compare the efficacy of early platelet inhibition
by 600 mg clopidogrel and acetylsalicylic acid (ASA) to a triple therapy including
a glycoprotein IIb-IIIa receptor blocker. Immediate percutaneous coronary intervention
(PCI) is recommended for high-risk acute coronary syndromes. In this setting the efficacy
of platelet inhibition is unknown. One hundred patients were randomized to receive
ASA and 600 mg clopidogrel, or additional open-label tirofiban (bolus of 10 µg/kg
body weight followed by continued infusion of 0.15 µg/kg body weight per minute) as
soon as non-ST - segment elevation myocardial infarction was diagnosed. The primary
endpoint was the reduction of infarct size determined by post-interventional increases
of cardiac troponin T (cTnT). Secondary endpoints included platelet function measured
by optical and impedance aggregometry using ADP (5 and 20 µM) and collagen (1 µg/ml)
as platelet agonists. Tirofiban maximized platelet inhibition (p<0.0001) immediately
and was associated with significantly lower post-interventional cTnT concentrations
(p=0.0352). In the dual platelet inhibition arm, clopidogrel was not effective in
69% of patients at the time of coronary intervention, and still in 47%, if pre-treatment
time was >120 minutes. The frequency of cardiovascular (death, myocardial infarction,
revascularization) and bleeding events was comparable. Platelet aggregation is not
adequately inhibited in cTnT - positive patients in the setting of immediate PCI with
very short pre-treatment times. Only tirofiban provided consistent and effective inhibition
of platelet aggregation at the time of immediate or very early invasive therapy.
Keywords
Platelets - myocardial infarction - angioplasty - inhibitors
