Abstract Body (Do not enter title and authors here): Introduction
Outpatient cardiac rehabilitation (CR) improves outcomes for patients with cardiac disease but has an historically low participation rate. For socioeconomically disadvantaged patients experiencing challenges with access to care, participation can prove especially difficult. The ERA-Nudge trial aimed to evaluate the effect of choice of hospital or home-based CR and the effect of behavioral nudge messaging on participation and adherence in a diverse population of low socioeconomic status. This is the first report of patient characteristics from ERA-Nudge.

Methods
ERA-Nudge was a pragmatic, randomized, controlled clinical trial using a 2x2 factorial design conducted at an urban safety net hospital in the US mountain west from 2019 to 2023. Patients were required to be eligible for CR, have a smartphone in order to use a mobile phone app, speak English or Spanish, and provide informed consent to participate in the study. At their baseline visit, patients were randomized to 1) choice of hospital or home-based CR with nudges; 2) choice of hospital or home-based CR alone; 3) hospital-based CR with nudges; 4) hospital-based CR alone. At study-required baseline, 6-week, and 12-week visits, clinical and lifestyle outcomes were assessed. Descriptive analyses were conducted on the characteristics of randomized patients.

Results
Among 697 screened patients who were eligible for CR, 517 consented to participate. There were 70 patients who were not randomized (22 no showed for baseline visit; 2 died before randomization; 1 withdrew; 45 could not be re-contacted or did not provide a reason), resulting in 447 patients randomized in the study (Table 1) and 316 that completed the three study-required visits.

Conclusions
ERA-Nudge was completed in a diverse, low-income, urban population, supporting the feasibility of evaluating smartphone and mobile app interventions in these patients. Not only did patients enroll, but most completed required study visits. Further analysis of the ERA-Nudge data will provide insight into how these patients responded to nudge-based mobile messaging, and whether having a choice to participate in CR at home impacted their overall CR adherence.

Registration Number: NCT03834155