Children and adolescents with inherited cardiac arrhythmia su ch Long QT Syndrome (LQTS) have lower physical and quality of life than their healthy peers. A multi-component cardiac rehabilitation, including an exercise training program and education program, might counteract those effects.

The goal of this pilot study is to evaluate the security, feasibility, and benefits of a cardiac rehabilitation program in children with LQTS aged between 6 to 18 years old.

The main question[s] it aims to answer are:

• Is center-based cardiac rehabilitation safe and feasible for children with LQTS?
• Does a 12-week cardiac rehabilitation program improve physical fitness and quality of life?

Physical fitness is an independent predictor of all-cause mortality and global health in the general population. Assessments of cardiorespiratory and muscle fitness in children with chronic illness are growing in interest, even in less prevalent chronic diseases. For instance, children and adolescents with Long QT Syndrome (LQTS) have lower cardiorespiratory fitness, muscle strength, and quality of life than their healthy peers.

A multi-component cardiac rehabilitation including an exercise training program and education program might counteract this lowered physical fitness.

The RYTHMO'FIT pilot study seeks to test the security, and feasibility, and to evaluate the benefits of an innovative center-based program to improve physical and mental health in children and adolescents with LQTS.

In this retrospective study, eight children had undergone a 12-week program, within each session composed by:

• A 1-hour exercise training session with a trained exercise physiologist: resistance training, aerobic training, stretching, and different activity (e.g., basketball, handball, football, hockey)
• A 30-min educational workshop with a specialist nurse (e.g., beta-blockade, sports participation, healthy behaviors).
• A 10-min medical interview with a cardiologist to have feedback from parents and patients on each session and the past 7 seven days.

We hypothesized the RYTHMO'FIT study is safe, feasible, and provides benefits for mental and physical health in children and adolescents with LQTS. If the results of this pilot study are positive, they will lead to a larger randomized multicentric controlled trial to evaluate the effectiveness of a hybrid cardiac rehabilitation program in children, adolescents, and young adults with LQTS.

• Children and adolescents, aged 6 to 18 years old, diagnosed with congenital LQTS and had been recently under medical check-up in our last study QUALIMYORYTHM
• With impaired cardiorespiratory fitness (VO2 peak <80% of predicted values or VAT <55% of predicted values) or with normal cardiorespiratory fitness but requiring patient education and information on limits/security in taking part in sports participation.
• Willingness and ability for parents and children to take part in a 12-week center-based program (e.g., availability during the school period, transportation options)
• Informed consent of parents or legal guardians, and oral assent of children.

Children aged 8 to 18 years with an LQTS.