The reason for the increased prevalence of blood clots is not known. A previous study investigated the prevalence of blood clots systematically in patients with cyanotic congenital heart disease and found that approximately 30-40% of the patients had had a clot in the lung or brain. Thus, the study could not predict, when the patient had had a thrombotic event, and most of the patients did not previously had imaging performed. Therefore the aim of this study is to re-examine previously examined cyanotic patients regardless of previous medical history, to assess how many of the patients have obtained additional blood clots since they were examined 8 years ago.