Platelet function and composition in heart transplant recipients compared with nontransplanted coronary patients

Abstract

Accelerated coronary artery disease seems to be the main condition limiting long-term survival after heart transplantation. Ninety-one heart transplant recipients were compared with 94 nontransplanted coronary artery disease patients in an attempt to identify the factors responsible for the accelerated form of coronary artery disease occurring after heart transplantation. Among the parameters examined, heart transplant recipients exhibited a higher plasma level of insulin (8.5±0.5 versus 6.2±0.3 mIU/1, p=0.002), a lower plasma level of vitamin E (14.8±0.4 versus 16.9±0.7 mg/l, p=0.03), a higher platelet cholesterol-to-phospholipid ratio (8.9±0.3 versus 7.6±0.3, p=0.007), and an increased response to ADP-induced platelet aggregation (for the first wave, 29.1±0.9% of maximal aggregation versus 25.1±1.0%, p=0.002; for the second wave, 21.4±1.4% versus 15.9±1.1%, p=0.002, after adjustment for hematocrit), but no untoward changes in the level of fibrinogen, plasminogen activator inhibitor-1, antithrombin III, or lipoprotein(a). In addition, platelet aggregation in patients who required retransplantation as a result of severe coronary artery disease was similar before and after retransplantation. This suggests that severe coronary artery disease is not the cause of platelet hyperaggregability. In multiple-regression analysis, ADP-induced platelet aggregation in heart transplant recipients was significantly positively related to blood glucose (r=0.50, p<0.001) and inversely related to n-3 fatty acids from platelet phospholipids (r=0.40, p<0.01). These results are consistent with the view that a platelet disorder associated with or responsible for the increased thrombotic tendency could play a role in the pathogenesis of the disease. However, further studies are needed to investigate the mechanism of this platelet hyperaggregability, which is possibly related to a lipid peroxidation process (low plasma vitamin E) and/or to a diabetes-associated platelet lipid disorder (high insulin level).