Congenital heart disease, with a wide spectrum of severity, affects approximately 1% of all live births. The majority of congenital cardiac structural abnormalities occur in otherwise healthy children and total correction of the cardiac lesion usually results in a normal productive lifespan. Thromboembolic disease has been termed the new epidemic of paediatric tertiary care hospitals. Nowhere is this more evident than in cardiac and cardiac surgical patients. Improved survival for these patients over the last decade has been the result of tremendous advances in surgical techniques, availability of new drugs and new applications for old drugs, and developments in critical and supportive care. Despite this, one of the most frequent complications seen in survivors of congenital heart disease is thromboembolism, which include venous, arterial, and intracardiac thrombosis, pulmonary embolus, and embolism to the central nervous system (CNS) (fig 1⇓). Venous thromboembolic disease in children with congenital heart disease has a mortality of approximately 7%. Morbidity in the form of post-phlebitic syndrome (fig 2⇓) and recurrent venous thrombosis occurs in over 20% of children. Figure 1 Magnetic resonance image of the brain demonstrating extensive ischaemic infarction caused by emboli from intracardiac thrombosis. Figure 2 Post-phlebitic syndrome in a teenage girl, cured of her underlying cardiac anomaly. Her initial thrombosis was asymptomatic and secondary to venous access for cardiac catheterisation. Her course has been complicated by two episodes of venous ulceration, each of which took over four months to heal. Infants and children with congenital heart disease constitute a major proportion of paediatric patients seen in tertiary hospitals with thromboembolism. Recent data show that almost 50% of infants less than 6 months old, and 30% of older children who suffer venous thromboembolic disease have underlying cardiac disorders. Similarly, almost 70% of infants (< 6 months) and 30% of children who suffer arterial thromboembolism have …