Platelet trapping in myocardial infarct in baboons: Therapeutic effect of aspirin

Blood platelet trapping has been demonstrated in the area of evolving myocardial infarction in baboons. Sixteen baboons were subjected to ligation of the diagonal branch of the left anterior descending coronary artery, and the extent of myocardial ischemia was monitored with a 64 to 72 electrode epicardial electrocardiographic grid. Eight animals received no treatment and eight were pretreated twice (at 12 hours and at 2 hours before ligation) with aspirin, 600 mg orally. Measurement of infarct extent included all electrode points with S-T segment elevation of 2 mV or greater. Chromium-51-tagged autologous platelets were injected 15 minutes before ligation. In all animals an area of ischemia developed in which typical changes evolved in S-T segments. In three of the eight aspirin-treated animals, double ligation was carried out. Aspirin was administered after release of the first ligature but before religation, and the area of S-T segment elevation was reduced by as much as 23 percent after aspirin treatment. Platelet trapping outside the area of S-T elevation was seen in 25± 3 percent of the total wall samples in aspirin-treated animals compared with 44 ± 7 percent of those in control animals (p