Abstract:Background: Congenital heart diseases (CHDs) are the most common type of birth defects. Improvements in CHD care have led to ~1.4 million survivors reaching adulthood. Thus, successful transition and transfer from pediatric to adult care is crucial. Unfortunately, <30% of adults with CHD successfully transition to adult care; this number is lower for minority and lower socioeconomic status (SES) populations. Few CHD programs exist to facilitate successful transition. Objective: To describe the development of a prototype mobile application (app) for CHD adolescents to facilitate transition.Methods: A literature search regarding best practices in transition medicine for CHD was conducted to inform app development. Formative research with a diverse group of CHD adolescents and their parents was conducted to determine gaps and needs for CHD transition to adult care. As part of the interview, surveys assessing transition readiness and CHD knowledge were completed. Two adolescent CHD expert panels were convened to inform educational content and app design.Results: Literature review revealed 113 articles, of which 38 were studies on transition programs and attitudes and three identified best practices in transition specific to CHD. Adolescents (n=402) participating in semi-structured interviews were 15-22 years old (Median age 16 years), female (42%), and racially/ethnically diverse (12.6% African American; 37.4% Latino. 36.4% received public insurance. Most adolescents (76.7%) had moderate or severe CHD complexity and reported minimal CHD understanding (79.2% aged 15-17 years and 61.5% aged 18-22 years). Average initial transition readiness score was 50.9/100, meaning that transition readiness training was recommended. A subset of participants (n=363) were asked about technology use: 94.5% reported having access to a smartphone. Interviews with parents revealed limited interactions with the pediatric cardiologist with transition-related topics: 79% reported no discussions regarding future family planning, and 55% reported the adolescent had not been screened for mental health concerns (depression, anxiety). Further, 66% reported not understanding how health care changes as adolescents become adults. Adolescents in the expert panel (n=6 total; two groups of n=3) expressed interest in a CHD-specific tailored app consisting of quick access to specific educational questions (e.g., "can I exercise"), a CHD story-blog forum, a mentorship platform, a question and answer space, and a transition checklist to facilitate transition. They expressed interest in using the app to schedule CHD clinic appointments and medication reminders. Based on this data, a prototype mobile application was created to assist in adolescent CHD transition.Conclusions: Formative research revealed that most adolescents with CHD had access to smartphones, were not prepared for transition to adult care, and were interested in an app to facilitate transition to adult CHD care. Understanding their needs, interests, and concerns will lead to the de...