Platelet hyperactivity in thalassemia patients with elevated tricuspid regurgitant velocity and the association with hemolysis

Abstract

IntroductionPulmonary arterial hypertension is a life-threatening complication in thalassemia characterized by elevated pulmonary arterial pressure. Increased platelet activation is associated with this complication; however, its role remains unclear. MethodsPlatelet activation in splenectomized β-thalassemia/hemoglobin E (Hb E) patients was measured using flow cytometric determination of P-selectin and activated glycoprotein (aGP) IIb/IIIa expression, and platelet-leukocyte aggregates (platelet-neutrophil, platelet-monocyte and platelet-lymphocyte aggregates). Tricuspid regurgitant velocity (TRV) was measured and used as an indicator of pulmonary arterial pressure. Plasma hemoglobin served as markers of hemolysis. ResultsFifteen of 27 patients had elevated TRV (>2.5m/s). Platelet expression of P-selectin and aGPIIb/IIIa, and platelet-leukocyte aggregates were higher in thalassemia patients with elevated TRV than healthy control. Platelet-neutrophil aggregates increased in thalassemia patients with elevated TRV compared to patients with normal TRV. The increase in P-selectin and aGPIIb/IIIa expression induced by adenosine diphosphate (ADP) was higher in patients with elevated TRV than those with normal TRV. Platelet P-selectin expression and platelet-neutrophil aggregates correlated positively with TRV. Plasma hemoglobin levels in patients with elevated TRV were higher than those of the control subjects, and correlated with TRV. ConclusionThalassemia patients with elevated TRV have a further increase in platelet activation that correlates with hemolysis.