Evaluation of the effects of catheter sampling for the study of platelet behavior in the pulmonary and coronary circulation

Abstract

To study the effects of sampling through cardiac catheters on indices of platelet function, we measured the levels of platelet factor 4 (PF 4), beta thromboglobulin (BTG), and platelet aggregate ratio (PAR) in 10 patients with atrioventricular accessory pathway (AVNAP), six patients with primary pulmonary hypertension (PPH), and six patients with critical narrowing of the left anterior descending artery (LAD). In AVNAP and LAD patients samples were drawn simultaneously from a peripheral vein, coronary sinus, and brachial artery; in AVNAP patients samples were also obtained from the axillary vein before the coronary sinus was entered. In PPH patients samples were drawn from pulmonary artery, aorta, and a peripheral vein; in these patients the effects of an intravenous infusion of prostacyclin (PGl 2) (2 to 8 ng/kg/min) on PF 4, BTG, and PAR were also studied at all sampling sites. In all patients arterial, coronary sinus, pulmonary arterial, and axillary venous levels of PF 4, BTG, and PAR significantly exceeded those measured in the peripheral vein. PGl 2 infusion resulted in a significant decrease of PF 4 at all sampling sites, while no consistent BTG changes were observed and PAR levels did not decrease in the peripheral vein. Although a considerable interpatient variability in PF 4 levels was observed, a significant ( r = 0.91) correlation was found in patients with AVNAP between simultaneous coronary sinus and arterial PF 4 levels. The value of PF 4 coronary sinus-arterial difference in LAD patients was consistently higher than that calculated in AVNAP patients (54.5 ± 28.9 vs 4.2 ± 3.8 ng/ml). In conclusion: (1) a considerable and variable degree of platelet activation occurs with catheter sampling, preventing the measurement of absolute levels of platelet metabolites; (2) among the indices examined PF 4 appears the most sensitive for detecting changes in platelet activity; and (3) the measurement of coronary sinus-arterial PF 4 differences may provide information on directional changes in transcardiac platelet behavior.