Chronic hypoxaemia and decompensated erythrocytosis in cyanotic congenital heart disease.

Among forty adults with cyanotic congenital heart disease there was a subset of eleven patients with especially pronounced erythrocytosis, repeatedly rising haematocrit, recurring symptoms of hyperviscosity, and little or no shift of the haemoglobin/oxygen-dissociation curve. These patients were iron deficient as a result of many therapeutic phlebotomies; nevertheless their red-cell mass was comparable to that in iron-replete patients with similar, but stable, haematocrits. Iron repletion in the deficient patients resulted in rapidly increasing haematocrit and hyperviscosity. In one extreme case, erythropoiesis remained persistently iron deficient despite normal serum iron and ferritin levels. "Decompensated erythrocytosis" is an apt term for the excessive erythrocytic response and the associated phenomena.