The Platelets in Cyanotic Congenital Heart Disease

The mean platelet count in 102 children with congenital cyanotic heart disease was found to be 235,000/mm3 ± 1 S.D. of 85,000/mm3 as compared to 260,000 ± 70,000 in an age-matched group of normal children. In the cyanotic children, whose mean oxygen saturation was >80%, the mean platelet level was 315,000/mm3 as compared to 185,000/mm3 in the <60% oxygen saturation group. The platelet means were inversely related to the mean hemoglobins, such that the mean hemoglobin in the >80% oxygen saturation group was 13.2 gm/100 ml as compared to 17.2 in the <60% group. The age of the patient, and thus the duration of the disease, was also related to the platelet levels with significantly higher platelet counts in the children under 3 years of age. The mean age of the patients with platelet counts below 100,000/mm3 was 4.7 years as compared to a mean age of 2.8 years in the patients with platelet levels greater than 400,000/mm3. In addition, the older children had the highest hemoglobins and the lowest oxygen saturations. The inverse was true for the thrombocytotic individuals. The level of bound iron was not related to the platelet levels; nor were there any associated marrow or suspected capillary changes. It appears that the initial response to oxygen undersaturation is a platelet stimulation which subsequently results in underproduction as oxygen desaturation persists and worsens.