The goal of this study is to collect quantitative and qualitative data that can be used to optimize the HeartSteps mHealth intervention for physical activity. The current version of the intervention is intended to help patients with heart disease increase and maintain their physical activity long-term. To accomplish this goal, a 3-month pilot micro-randomized trial (MRT) will be conducted with 60 patients who are currently completing or have recently completed phase II cardiac rehabilitation (CR).

The core of the study participation is the use of the HeartSteps intervention over the course of 3 months. This includes wearing the Fitbit Charge activity tracker during waking hours and using the HeartSteps intervention to support their efforts to be active. The HeartSteps intervention consists of two sets of intervention components: (1) components intended to improve participants' affective associations with physical activity, including activity suggestions designed to to trigger positive feelings and associate them with being active, and prompts to bring their awareness to intrinsically motivating aspects of being active; and (2) components that target reflective self-regulatory processes, including graphs for self-monitoring, prompts to plan activity, and weekly activity goals. How exactly, and how much, participants will use HeartSteps will not be prescribed since our goal is to understand naturalistic trajectory of engagement with the intervention.

Inclusion Criteria:

• Must be a patient within the Michigan Medicine clinical system with data available in the electronic health record after January 1, 2020.

• Age > 18

• Owns and is a daily user of an Android or iPhone smartphone with study supported operating software.

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

• Will be completing within 30 days or have completed in the last 30 days the cardiac rehabilitation program at Michigan Medicine based on one of the following indications:

  • 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:

• Orthopedic or neurological condition limiting ability to actively engage in moderate intensity physical activity (e.g., brisk walking)
• Greater than mild cognitive impairment
• Wrist too large to wear an activity tracker 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."
• Currently receiving palliative care and/or in hospice care
• Severe valvular stenosis or regurgitation
• Unrevascularized left main coronary artery disease (> 50% obstruction on angiography) or proximal left anterior descending disease (>70% obstruction on angiography).
• Exercise-induced ventricular tachycardia
• Cardiac arrest within the prior 6 months
• New York Heart Association (NYHA) class III or IV heart failure
• Pulmonary arterial hypertension treated with inhaled or intravenous pulmonary hypertension-specific therapy
• Ejection fraction <40%
• Determined to be unsafe for participation in this program as assessed by a clinical nurse or investigative team.