ASPIRIN, BUT NOT HEPARIN, SUPPRESSES THE TRANSIENT INCREASE IN THROMBOXANE BIOSYNTHESIS ASSOCIATED WITH CARDIAC-CATHETERIZATION OR CORONARYANGIOPLASTY

Objectives. We sought to study the dose dependence of in vivo suppress ion by aspirin of enhanced thromboxane biosynthesis in the setting of coronary angioplasty and to evaluate the effects of heparin and aspiri n during cardiac catheterization. Background. Percutaneous translumina l coronary angioplasty induces a controlled injury of the intima of th e diseased arterial segment, with rapid deposition of platelets at the site of dilation. Thus, it provides a clinical model of intracoronary platelet activation. Methods. The urinary excretion of a major enzyma tic metabolite of thromboxane A2, 11-dehydro-thromboxane B2, was measu red in 57 patients with stable coronary artery disease undergoing card iac catheterization (n = 28) or elective single-vessel percutaneous tr ansluminal coronary angioplasty (n = 29). Three consecutive urine coll ections were obtained from all patients before during and after either procedure. Patients undergoing catheterization were treated with the following regimens: a) no aspirin for greater-than-or-equal-to 10 days and no heparin (n = 12); b) no aspirin for greater-than-or-equal-to 1 0 days but heparin, 10,000 IU, at the time of catheterization (n = 5); c) aspirin, 300 mg/day, for at least 5 days (n = 11). Patients underg oing coronary angioplasty were randomly assigned to short-term treatme nt with aspirin given as a) 75 mg/day for greater-than-or-equal-to 5 d ays before angioplasty (n = 11); b) 300 mg/day for greater-than-or-equ al-to 3 days before angioplasty (n = 9); or c) 300 mg/day for greater- than-or-equal-to 3 days before angioplasty followed by 1,000 mg during angioplasty (n = 9). Results. In patients undergoing catheterization, urinary 11-dehydro-thromboxane B2 excretion (pg/mg creatinine) increa sed from 563 +/- 481 (mean +/- SD) to 1,684 +/- 1,332 in the absence a nd from 620 +/- 191 to 1,588 +/- 597 in the presence of heparin. No in crease was observed in the group receiving aspirin (from 240 +/- 141 t o 215 +/- 115). In patients undergoing coronary angioplasty treated wi th aspirin, 75 mg/day, urinary 11-dehydro-thromboxane B, averaged 180 +/- 112, 223 +/- 178 and 294 +/- 260, respectively, before, during and after the procedure. At 300 mg/day, the corresponding values were 185 +/- 48, 217 +/- 70 and 197 +/- 93. In patients also receiving aspirin , 1,000 mg, during angioplasty, 11-dehydro-thromboxane B2 averaged 151 +/- 66, 138 +/- 43 and 133 +/- 77, respectively. Conclusions. Enhance d thromboxane biosynthesis associated with cardiac catheterization or coronary angioplasty can be largely suppressed by low dose aspirin. Th is finding is consistent with the view that this alteration reflects p latelet activation.