Word count: 3014 What is already known about this topic?  Infective endocarditis (IE) is infrequent in children and adolescents.  Congenital heart defects (CHDs) represent the major risk factor for IE today.  CHDs is a risk factor for increased mortality and complications in patients with IE. What does this study add?  This nationwide study reports an incidence of IE of 2.2 per 10 000 person-years among children and adolescents with CHDs.  Most patients with IE had severe CHDs and had

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... gone open chest cardiac surgery or catheter-based cardiac interventions the last year before IE.  The IE related mortality among children with CHDs and IE was 8% during the followup period. Abstract Objectives Congenital heart defects (CHD) are the most common birth defects worldwide and are an important cause of morbidity and early death. A significant number of deaths occur among patients with infections. CHDs predispose subjects to the development of infective endocarditis (IE) and represent a risk factor for increased mortality due to IE. The aims of this study were to investigate the occurrence and outcomes of IE in children and adolescents with CHDs. Methods Data concerning all children with CHD and IE born in Norway between 1994 and 2016 were retrieved from the Oslo University Hospital's Clinical Registry for Congenital Heart Defects. Survivors were followed through 2016, and supplementary information was retrieved from medical records. Results In this nationwide register-based cohort study, which included all 1 357 543 live births in Norway between 1994 and 2016, the incidence of IE according to the European Society of Cardiology diagnostic criteria, was 2.2 per 10 000 person-years among children and adolescents with CHDs. The incidence was stable throughout the period. Most patients with IE had severe CHDs (75%) and had undergone open chest cardiac surgery or catheter-based cardiac interventions the last year before IE. IE-related mortality among children with CHDs and IE was 8% during the follow-up period (mean 12.4 years (5.5 years)). Conclusions