Professor Gérald Simonneau, MD, Hôpital Kremlin Bicêtre, Paris-Sud University, France.
Until recently, the prevalence and characteristics of pulmonary hypertension (PH) in adults with sickle cell disease remained uncertain. In previous studies, the prevalence of PH, as defined by a tricuspid valve regurgitant jet velocity (TRJV) of ≥ 2.5 m s -1 , has been reported as high as 30%. However, in these studies, the diagnosis of PH was not systematically confirmed on right heart catheterisation (RHC), a proceure that is recommended in international guidelines as the standart of care. The use of RHC also makes it possible to accurately distinguish between pre-capillary and post –capillary PH , which is especially important in this setting , since the presence of post-capillary PH due to associated left heart disease has been frequently reported in adult patients with sickle cell disease.
Two recent perfomed in France and in Brazil have shown a prevalence of PH of 6.2 % and 10 %, respectively, lower than expected. Interestingly, post-capillary PH was the most frequent cause, with a prevalence of 3.3% and 6.2 %, respectively, whereas the prevalence of pre-capillary PH was only 2.9% and 3.8%. In addition, these two studies clearly demonstrate that, when a threshold TRJV of studies clearly demonstrate that, when a threshold TRJV of ≥2.5 s -1 was used to define PH, the positive predictive value of echocardiography for detection of PH was only 25% and 32 % respectively. Furthermore, pre-capillary PH associated with sickle cell disease appears quite different from the other forms of PAH in terms of both its haemodynamic profile and response to specific PAH therapies. These observations call into question the rationale for keeping sickle cell disease In group 1 (PAH) of the clinical PH classification system.