Experimental: Cardiac rehabilitation

For patient randomized to cardiac rehabilitation, the ACHD clinician will place the referral after they and the patient have seen the group assignment. All participants will be referred to Heart Fit for Life community-based cardiac rehabilitation program in Palo Alto, CA. Cardiac rehabilitation will be offered as an in-person, hybrid, or completely virtual program for Stanford participants and will be entirely virtual for Vanderbilt participants. Participants will attend 3 sessions per week for 12 weeks. Participants will receive weekly email reminders via the electronic medical record to encourage participation. The study protocol pertains only to referral to cardiac rehabilitation. All other aspects of the cardiac care will be at the discretion of clinicians. All study participants will receive a Fitbit for daily activity tracking.

Active_comparator: Usual care

For patients randomized to the usual care (no cardiac rehabilitation group), cardiac rehabilitation will not be initiated between randomization and for up to 16 weeks following randomization. The study protocol controls only referral to cardiac rehabilitation. All other aspects of the cardiac care, such as titration of guideline directed medical therapy will be at the discretion of clinicians. All study participants will receive a Fitbit for daily activity tracking.