The hypothesis of this study is that participation in a formal cardiopulmonary rehabilitation program improves aerobic exercise capacity and quality of life over the medium term for patients with congenital heart disease with reduced exercise capacity. To test this hypothesis, subjects will be randomized to either receive a 12-week cardiopulmonary rehabilitation program or standard of care, with interval testing of aerobic capacity and other physiologic markers improved fitness, as well as assessment of quality of life.

Inclusion Criteria:

• Able and willing to participate in a 12-week cardiac rehabilitation program and repeated cardiopulmonary exercise testing
• pVO2≤80% predicted (impaired aerobic capacity) on baseline exercise test
• congenital heart disease of at least moderate complexity

Exclusion Criteria:

• Cardiac intervention (cath/surg) within prior 6m
• Planned cardiac intervention (cath/surg) within 12m
• Formal cardiac rehabilitation within 24m
• Current/recent (delivery<90d prior) pregnancy, planned pregnancy within 12m
• Active heart failure, hospitalization or major change in clinical status over prior 30d
• Other recent or planned events expected to have a significant impact on exercise capacity
• Baseline oxygen saturation <92%