Thromboxane A2 may play a role in coronary arterial spasm, unstable angina, myocardial infarction, cardiac arrhythmias, and sudden death. Although previous studies have examined peripheral, aortic, and coronary sinus concentrations of its stable metabolite, thromboxane B2 (TxB2), it is unknown, first, if blood sampling through long catheters alters the concentration of TxB2 and second, if peripheral levels of this prostanoid reflect its intracoronary production and release. In order to answer these questions, paired blood samples were obtained through an 18-gauge needle and a No. 7 or 8 French 110 to 125 cm catheter from the arterial (14 patients) and venous (16 patients) circulations; in addition, coronary sinus and peripheral venous samples were obtained in 16 patients and aortic samples were obtained in 14 of these patients. All samples were analyzed to TxB2 by radioimmunoassay. Blood sampling through long catheters did not systematically alter the concentrations of arterial TxB2 (needle, 85.5 +/- 67.5 pg/ml [mean +/- SD]; catheter, 62.3 +/- 40.9 pg/ml; p = 0.20) or venous TxB2 (needle, 182.5 +/- 170.5 pg/ml; catheter, 521.4 +/- 1536.0 pg/ml; p = 0.39). Peripheral venous TxB2 levels did not correlate with TxB2 levels in coronary sinus (r = 0.01) or the TxB2 coronary sinus/aortic ratios (r = 0.21). Thus blood sampling through long catheters across the coronary bed is both a reliable and necessary method for assessing intracoronary TxB2 production in patients with ischemic heart disease.