The researchers are trying to determine whether a smartwatch and a mobile application, which together deliver activity and goal setting notifications, can increase activity levels for patients enrolled in cardiac rehabilitation.

The VALENTINE Cardiac Rehabilitation Study will evaluate a digital intervention to supplement cardiac rehabilitation for low- and moderate risk patients, integrating a mobile application with physiologic and contextual information from wearables to provide incremental support to patients. The study will be performed in conjunction with planned home-, hybrid-, or center-based cardiac rehabilitation at Michigan Medicine. Participants will be randomized to the control or telehealth group. Both groups will receive a smartwatch and usual care. Participants in the telehealth arm will additionally (1) have access to activity tracking and goal setting through the VALENTINE app; (2) receive micro-randomized, contextually tailored notifications, and (3) receive weekly activity summaries via email, which will also be provided to their exercise physiologist while enrolled in cardiac rehabilitation. Contextually tailored notifications will be one of two types: walking and exercise notifications. Walking notifications are designed to encourage participants to be active though at lower than their target heart rate zone. Participants will receive 1 notification per day, on average, at one of four times. Notifications will be randomized on four dimensions of context. Exercise notifications are designed to encourage participants to exercise within their target heart rate zone. Notifications will be delivered each evening at a time of the participant's choosing. Participants will have a 50% probability of receiving a notification each evening. Notifications will be randomized on two dimensions of context. Participants will be followed for 6-months. Participants in both arms will be asked to complete a 6-minute walk test at baseline, 3-months, and 6-months using their mobile phone and smartwatch. They will additionally complete general and disease-specific quality-of-life questionnaires at baseline and at 6-months.

To account for potential measurement error between devices, for primary and secondary analyses, we will perform regression analysis to jointly test the null hypothesis H0: B0(F) = B0(A) = 0 for change between baseline and 6 months where (F) and (A) refer to Fitbit and Apple watches respectively. A secondary analysis will subsequently be performed to determine whether to reject the individual null hypotheses for each of the two devices. For all statistical analyses, the level of significance will be set at p <0.05.

Inclusion criteria:

1. Must be a patient within the Michigan Medicine clinical system with data available in the electronic health record after January 1, 2013. Spectrum Health patients may participate if they have a Michigan Medicine MRN and data is available through connected electronic health records.

2. Age > 18 and < 75

3. Owns an Android or iPhone with study supported operating software.

4. Understands English to enable informed consent, completion of study-related surveys, and compliance with study notifications.

5. Enrolled in cardiac rehabilitation within the past 8-weeks based on one of the following indications (listed below) and has completed at least 2 cardiac rehabilitation sessions (includes orientation session; to remain in the study, participants in the hybrid program must complete at least one additional exercise session for a minimum of 2 center-based rehabilitation sessions):

   • Coronary artery disease (including acute coronary syndromes and stable angina) following percutaneous coronary intervention (PCI)
   • Coronary artery disease following coronary artery bypass surgery (CABG)]
   • Valve repair or replacement (either surgical or percutaneous)
   • Coronary artery disease or an acute coronary syndrome not requiring revascularization

Exclusion criteria:

1. Orthopedic or neurological condition limiting ability to actively engage in exercise training session
2. Greater than mild cognitive impairment
3. Wrist too large to wear a smartwatch comfortably. This will be assessed by asking participants "If they have ever had difficulty wearing a watch in the past due to the band being too small."
4. Currently receiving palliative care and/or in hospice care
5. Severe valvular stenosis or regurgitation
6. Unrevascularized left main coronary artery disease (> 50% obstruction on angiography) or proximal left anterior descending disease (>70% obstruction on angiography).
7. Exercise-induced ventricular tachycardia
8. Cardiac arrest within the prior 6 months
9. New York Heart Association (NYHA) class III or IV heart failure
10. Pulmonary arterial hypertension treated with inhaled or intravenous pulmonary hypertension-specific therapy
11. Ejection fraction <40%
12. Determined to be unsafe for participation in this program to augment cardiac rehabilitation as assessed by a clinical nurse or investigative team.