Thrombocytopaenia is common in adults with cyanotic heart disease. Our aim was to explore potential mechanisms for thrombocytopaenia in these vulnerable patients.

Adults with cyanotic heart defects were identified from our clinical database. Haemoglobin levels, platelet counts, and resting oxygen saturations were determined at baseline and during follow-up. Associations between patient characteristics and cardiac physiology with these parameters at baseline and during follow-up were analysed using regression models. Survival estimates were determined by the Kaplan–Meier method.

We included 79 patients (mean age 32.2 ± 12.4, 48 (61%) Eisenmenger syndrome, 20 (25%) Down syndrome). Mean oxygen saturation was 84.1 ± 5.9%; 38 (48%) had thrombocytopaenia. There was a strong inverse correlation between platelet count and haemoglobin level (R = −0.655, R2 = 0.429, p < 0.0001) and a weaker but significant positive correlation between platelet count and oxygen saturation (R = 0.345, R2 = 0.119, p = 0.002). There was a significant inverse correlation between decrease in platelet count and increase in haemoglobin level during follow-up (R = −0.401, R2 = 0.161, p = 0.001) but not to changes in oxygen saturation (R = 0.043, R2 = 0.002, p = 0.726). Survival estimates were lower for patients with thrombocytopaenia at baseline (log-rank test p < 0.0001).

Our findings suggest a direct inverse correlation between platelet counts and haemoglobin levels in adults with cyanotic heart disease. Further studies are required to explore the mechanisms of thrombocytopaenia in cyanotic heart disease and its potential role as an independent marker of risk.