Prevalence and Pathophysiology of Systemic Arterial Pressure Abnormalities in Childhood Sickle Cell Disease (DrépaPA)

It is usually found that the blood pressure of adults with sickle cell disease is lower than in non-sickle cell patients. On the other hand, three recent prospective studies in children with sickle cell disease show prevalence of hypertension diagnosed by ambulatory blood pressure measurement (ABPM) ranging from 32 to 45% but on small numbers of patients (n = 54 at most). This hypertension appears to affect kidney function and has been previously associated with the risk of hemorrhagic stroke. It is therefore important to know the prevalence of hypertension in children with sickle cell disease and to determine its mechanisms. The factors which could explain this high prevalence are the increase in arterial stiffness and the increase in systemic vascular resistance linked to the alteration of the sympathovagal balance contributing to the regulation of vascular tone. Indeed, a disturbance of this balance with an increase in vasoconstrictor sympathetic tone has already been found. Hypothesis: In a subgroup of sickle cell children there is systemic hypertension (prevalence: main objective) linked to the alteration of the sympathovagal balance already established during sickle cell disease (increase in sympathetic tone and decrease in parasympathetic tone) affecting systemic vascular resistance (secondary pathophysiological objectives).