The Canadian Fontan Connection (CANFON): Protocol for a National Lifespan Cohort of People Living With a Fontan Circulation

<h2>Abstract</h2> The life expectancy of people living with a Fontan circulation has improved significantly over recent decades. However, this population remains at risk of multiorgan complications and premature mortality with advancing age. Despite growing clinical experience, key knowledge gaps remain in our understanding of Fontan-related morbidity, including the timing, predisposition and progression of complications, their cumulative burden, and their long-term impact on quality of life and functional outcomes. To address these challenges, we establish CANFON, a national, longitudinal cohort of individuals with single ventricle physiology who are either eligible for or living with a Fontan circulation. The design and implementation of CANFON were developed through engagement with Canadian congenital heart disease experts and alignment with international research priorities. Comprehensive clinical data are collected and banked from birth onward, providing an in-depth, lifelong view of each participant's health. In parallel, participant-reported outcome measures are prospectively collected over a 5-year period. Recruitment occurs in 24 pediatric and adult congenital heart disease centers across Canada. The over-arching objectives of CANFON are to 1) establish the health trajectories of Fontan physiology across the lifespan, 2) determine the prevalence and evolution of complications and modifying factors, 3) identify early predictors and risk factors for Fontan failure, and 4) assess the impact of complications on quality of life and functional status through participant-reported outcomes. Beyond its immediate goals, CANFON will serve as a unique, well-phenotyped, pan-Canadian research platform to support nested studies and accelerate progress in understanding and improving outcomes for individuals living with a Fontan circulation nationally and internationally.