**Background:** Coronary artery disease (CAD) remains the leading cause of death worldwide, contributing to 16% of total mortality. Despite therapeutic advances, morbidity and mortality among patients with chronic coronary syndrome (CCS) remain high. Poor adherence to lifestyle modifications and pharmacological therapy is a major driver of adverse outcomes—70% of patients fail to make minimal behavioral adjustments after a cardiovascular event, only 40% reduce saturated fat intake, and only 35% increase fruit/vegetable consumption. Current ESC guidelines recommend multidisciplinary lifestyle management, but implementation is hampered by high clinical workloads and prolonged gaps between appointments. eHealth approaches using smartphone applications have shown promise: an early meta-analysis demonstrated positive effects on diet and physical activity, and a recent meta-analysis found eHealth interventions associated with lower rehospitalization and cardiac events. However, the MyHeartMate randomized controlled trial in 390 CAD patients found no improvement in risk factors or lifestyle behaviors other than triglyceride levels after 6 months. The CHANGE study addresses the need for further randomized evidence on digital secondary prevention in a European CCS cohort.
**Methods:** The CHANGE study is a prospective, randomized, controlled trial with 1:1 allocation, conducted across nine centers in Germany (two university hospitals in Bonn and Düsseldorf, a tertiary hospital in Trier, a secondary hospital in Cologne, and five cardiology specialist practices). A total of 210 patients with CCS (ICD-10: I25) will be enrolled. Inclusion criteria: age ≥18 years, diagnosis of CCS, understanding of the study protocol, and written informed consent. Exclusion criteria are device-related (no compatible smartphone, inability to use the app, insufficient German language proficiency) and study-related (participation in another clinical trial, planned or recent CAD rehabilitation within 2 months, conflict of interest). The intervention group receives the VantisTherapy* app plus standard-of-care; the control group receives standard-of-care alone. The app provides a daily plan including video-guided home exercises tailored to patient capabilities, medication tracking, educational units, digital nutrition coaching based on Mediterranean diet guidelines, home blood pressure monitoring via a connected Bluetooth device (Omron HEM-7155T-D or similar), bodyweight recording, symptom tracking (e.g., angina pectoris), and a simulated 'heart age' summarizing therapy progress. The app uses game design elements, positive reinforcement, and small attainable goals to enhance adherence. Outcomes are assessed at three in-person visits: baseline (V0, week 0), V1 (week 12 ± 7 days), and V2 (week 24 ± 7 days). Primary endpoints are overall adherence to secondary prevention recommendations (scored 0–4 or 0–4.5 points based on physical activity ≥150 min/week over ≥5 days, Mediterranean Diet Adherence Screener [MEDAS] score ≥8, smoking cessation in past 14 days, Morisky Medication Adherence Scale-4 [MMAS-4] score of 4, and home blood pressure monitoring ≥8/14 days if indicated) and quality of life measured by the HeartQoL questionnaire. Secondary endpoints include adherence and QoL changes at 12 weeks, changes in systolic/diastolic blood pressure (if baseline >139/>89 mmHg), LDL-cholesterol (if baseline >55 mg/dL), heart rate (if baseline >50 b.p.m.), BMI (if baseline >25 kg/m²), and app usage patterns (dropouts: 0/14 days, irregular: 1–6/14 days, regular: ≥7/14 days). Statistical analysis uses intention-to-treat with analysis of variance for repeated measures. With alpha = 0.025 (two-sided), 80% power, and 1:1 allocation, 92 patients were calculated for the adherence endpoint and 210 for the QoL endpoint. An interim analysis will be performed after 70 patients complete V1. Recruitment started in July 2022; 110 participants had been recruited at the time of manuscript submission.
**Key Results:** This is a study protocol; no results are reported. The paper describes the rationale, design, and methods of the ongoing CHANGE study.
**Clinical Implications:** The CHANGE study will provide evidence on whether a smartphone-guided secondary prevention app combined with a monitor function can improve adherence to ESC guideline-based secondary prevention and quality of life in CCS patients compared to standard-of-care alone. If positive, the results could support the first reimbursable cardiological digital health app in Germany, addressing a critical gap in continuous, multidisciplinary lifestyle management between clinical appointments. The multicomponent app addresses physical activity, diet, smoking cessation, medication adherence, and home blood pressure monitoring simultaneously, potentially offering a scalable solution to the well-documented problem of poor adherence in secondary prevention.