Platelet microaggregation inhibition in patients with acute myocardial infarction pretreated with tirofiban and relationship with angiographic and clinical outcome.
BACKGROUND
The relationship between the level of platelet aggregation inhibition in patients with acute myocardial infarction and their clinical outcome is unknown.


METHODS
In patients with acute myocardial infarction included in the On-TIME trial and transferred to the primary percutaneous coronary intervention (PCI) center of Zwolle, who were pretreated with tirofiban on top of acetylsalicylic acid and heparin, platelet microaggregation inhibition was assessed on admission and immediately after PCI, using the Sysmex K4500 (Sysmex Corp, Kobe, Japan) platelet microaggregation measurement. The level of platelet microaggregation inhibition was compared with angiographic and clinical outcome. Patients were randomized to early prehospital initiation of tirofiban or to initiation in the catheterization laboratory. Therefore, the effect of tirofiban on platelet microaggregation inhibition could additionally be determined by measuring baseline platelet microaggregation also at entrance into the hospital.


RESULTS
In 412 (89%) of 463 patients, platelet microaggregation inhibition was measured after receiving tirofiban. There was no difference between the 4 quartiles of the level of platelet microaggregation inhibition with regard to distal embolization, TIMI-3 flow and blush grade 3 after PCI, mean corrected TIMI frame count, ejection fraction, enzymatic infarct size, and percentage ST-segment resolution (P values .91, .97, .46, .94, .73, .33, and .72, respectively). The baseline platelet microaggregation inhibition in patients treated with tirofiban was 38% +/- 25% (mean +/- SD), and in the patients treated with placebo, 14% +/- 22% (P < .001).


CONCLUSIONS
We found no correlation between the level of platelet microaggregation inhibition after tirofiban and outcome, whereas only a modest increase in platelet microaggregation inhibition was observed after a commonly used dose of tirofiban.
Smit
Jaap Jan J
JJ
Department of Cardiology, Isala Klinieken, Zwolle, The Netherlands.
Ernst
Nicolette M S K J
NM
Slingerland
Robbert J
RJ
Kolkman
J J Evelien
JJ
Suryapranata
Harry
H
Hoorntje
Jan C A
JC
Dambrink
Jan Henk
JH
Ottervanger
Jan Paul
JP
Gosselink
A T Marcel
AT
de Boer
Menko Jan
MJ
van 't Hof
Arnoud W J
AW
D000368:Aged; D015906:Angioplasty, Balloon, Coronary; D017023:Coronary Angiography; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000628:therapy*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use*; D000077466:Tirofiban; D016896:Treatment Outcome; D014443:Tyrosine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000627:therapeutic use
D010975:Platelet Aggregation Inhibitors; D014443:Tyrosine; D000077466:Tirofiban