To the Editor, We read with great interest the recent publication by Anderson et al.  on the inconsistencies in medication therapy among Fontan patients across seven pediatric heart networks in the United States. The practice in the United Kingdom appears to reflect a similar treatment dilemma. We conducted a survey of consultant pediatric cardiologists, with 20 respondents representing 13 different pediatric cardiology centers in the United Kingdom. The main variation in practice was that 80% of respondent paediatric cardiologists prescribed long-term aspirin after superior cavopulmonary anastomosis and 20% preferred not to use any treatment. In the first 6 months after completion of Fontan, warfarin was prescribed by 74% of respondents and aspirin by the remainder. However, beyond 6 months after Fontan, all the respondents provided anticoagulation prophylaxis, with 42% prescribing aspirin compared with 58% using warfarin. The issue of prophylactic anticoagulation for patients palliated with Fontan circulation is a recurring theme . Compelling data show that thrombotic events are a major cause of mortality among patients after Fontan surgery . Although the pathophysiology of thromboembolism in Fontan patients still is not clearly defined and we cannot reliably risk stratify each patient, the pharmacologic options for reducing thromboembolism do vary and have their own inherent risks. In the case of warfarin, a young person’s lifestyle choices also may be affected. We are awaiting data from the study on the efficacy of aspirin compared with warfarin anticoagulation in reducing the thromboembolic risk for Fontan patients . This study has the advantage of primarily including patients with lateral tunnel or extracardiac total cavopulmonary anastamosis and therefore is more relevant to the current era of surgical outcomes. However, this study may not adequately quantify the safety profile of long-term aspirin or warfarin nor is it likely to assess the impact on lifestyle and the psychosocial burden on children and young adults. We envisage that the decision making may become more complex with the newer generation of anticoagulants (direct thrombin inhibitors and direct factor Xa inhibitors), which are not as yet licensed for children. Their use may begin sporadically because they require little or no monitoring. Conducting a large well-designed multicenter prospective trial will provide more robust data but may not address every concern for Fontan patients. In the United Kingdom, setting up such a trial would be a challenge considering the small number of patients (151 survivors of Fontan surgery from 2008 to 2009 in the United Kingdom)  and the heterogeneity of the underlying cardiac morphology. We believe that establishing a UK Fontan registry will augment data from trials, improve understanding, allow comparison of variations in practice, and thus guide our future practice.