Current international guidelines recommend that patients with a heart pump (left ventricular assist device, LVAD) participate in supervised exercise cardiac rehabilitation programs. However, not all patients with a heart pump are able to attend to a supervised program on a daily basis.

The goal of this clinical trial is to determine whether a home-based exercise program helps patients with a heart pump improve their exercise capacity and quality of life, guided by telemedicine tools including a mobile app, smartwatch, and remote medical checkups. The study will also provide information about the safety of this program by monitoring for any issues or symptoms during home activity.

The trial aims to answer the following questions:

• Does a 12-week remote exercise program improve patients' exercise capacity? This will be measured using the 6-minute walk test and a cardiopulmonary exercise test.
• Is it safe for patients to follow this exercise plan at home while being monitored through a mobile app and smartwatch?
• Does the program improve quality of life and reduce feelings of anxiety or depression? This will be assessed using widely validated questionnaires, such as the Kansas City Cardiomyopathy Questionnaire.

Researchers will compare the remote exercise program to standard care, which usually does not include exercise for patients who are unable to attend the hospital daily.

Participants will:

• Join the study voluntarily after signing a consent form.
• Be randomly assigned, with a 50% chance of being in either the exercise group (following a structured plan with a mobile app) or the usual care group (receiving general written advice), to see which approach works best for recovery.
• Follow a 12-week home-based routine if in the exercise group, including warm-up routine, walking or cycling, respiratory exercises, and light strength training, all supported by the mobile app, smartwatch, and professional monitoring.
• Visit the hospital three times over six months for medical checkups, including walking and exercise tests, blood analyses, and questionnaires about physical and emotional health.

Introduction Although cardiac rehabilitation is recommended in patients with a durable Left Ventricular Assist Device (LVAD), approximately 50% of candidates cannot attend in-person programs due to geographical dificulties.

Study Rationale and Design The RE-ACTION-VAD Trial is the first multicenter randomized controlled trial designed to evaluate the efficacy and safety of a remote conditioning exercise program in patients with recent implantation of a durable Left Ventricular Assist Device (LVAD).

A total of 78 patients will be enrolled and randomized in a 1:1 ratio to:

1. Remote conditioning group: patients will undergo a three-month home-based program including aerobic, resistance, and respiratory training. Follow-up will be conducted through Telemedicine (mobile application and a smart watch); or
2. Usual care group: patients will receive written general exercise recommendations.

The primary objective is to assess whether there is an improvement in the distance covered on the 6-minute walk test at 6-month follow-up. Secondary objectives include evaluation of safety, and improvements in cardiopulmonary exercise parameters, quality of life questionnaires, frailty scales, and psychological questionnaires.

Intervention Logistics

The 12-week program is divided into an initial educational phase and a remote phase:

1. Educational Phase (Week 1): Three in-person sessions to train patients on exercise execution, load management, and the use of respiratory devices.
2. Remote Phase (Weeks 2-12): Individualized home routines including aerobic training, strength training, and respiratory.

Quality Assurance and Monitoring Plan

To ensure the integrity and standardization of the intervention across the 10 participating centers, the following quality measures are implemented:

• Site Monitoring: The study has contracted a Contract Research Organization (CRO), to perform clinical trial monitoring and auditing over a three-year period.
• Standardization of Procedures: Researchers from all centers are required to complete a rotation at the Hospital Ramón y Cajal Rehabilitation Unit to unify exercise protocols. Monthly supervision meetings are held to evaluate compliance and resolve clinical doubts.

Safety monitoring board: independent adverse event assessment blinded to the intervention group.

• Technical Validation: The mobile platform utilized for monitoring holds the requisite certifications, ensuring technical reliability and data security.

Data Management and Registry Procedures

• Data Entry and Validation: Data is captured using an electronic data capture system. The system includes predefined rules for data ranges and consistency to minimize entry errors.
• Source Data Verification (SDV): Investigators may cross-reference data from the electronic data capture system with hospital medical records to ensure accuracy, completeness, and representativeness.
• Data Dictionary: A comprehensive data dictionary is maintained within the study's electronic data management system, encompassing variables such as anthropometric measures, cardiopulmonary exercise test (CPET) parameters (VO₂ peak, VE/VCO₂, RER), 6-minute walk test (6MWT) distance, biomarkers (NT-proBNP, CA125), and validated quality-of-life scales (KCCQ, MLHFQ).
• Audit Trails: the electronic data capture system provides automated audit logs to track all data manipulations and user activity, ensuring full traceability.

Sample Size Assessment The study is powered to detect a clinically relevant difference of 35 meters in the 6MWT. Based on a standard deviation of 50 meters, an alpha of 0.05, and a power of 80%, 33 patients per group (66 total) are required. To account for an expected 15% dropout rate, the total sample size is set at 78 participants.

Statistical Analysis Plan (SAP) All analyses will follow the Intention-to-Treat (ITT) principle.

• Continuous Variables: Will be compared using the Student's T-test for independent samples or the Mann-Whitney U-test for non-parametric data.
• Categorical Variables: Will be analyzed using Chi-square or Fisher's Exact test.
• Missing Data Plan: While the ITT principle handles participants as randomized, the study also includes monthly supervision to incentivize compliance and minimize missing data.
• Significance: A p-value < 0.05 will be considered statistically significant.

Ethics and Confidentiality The protocol was approved by the Hospital Universitario Puerta de Hierro Ethics Committee (PI 143/25). Data is codified, and the link between codes and patient identity is stored in a password-protected offline file. Upon completion, anonymized data will be deposited in the Zenodo repository.

Inclusion Criteria (must meet all):

• Recent LVAD Implantation (<6 months)
• Clinical stability (defined as meeting all of the following criteria): discharge from the LVAD implantation hospitalization, absence of inotropic medication, hemoglobin >9 g/dL, and no active infection.
• Inability to participate in a supervised rehabilitation program (due to lack of availability, or inability because geographical reasons).

Exclusion Criteria (any):

• Functional Inability to Perform Cardiopulmonary Exercise Testing
• Prior Participation in a Supervised Rehabilitation Program (after the LVAD implantation)

Upon completion of the project and publication of the primary analysis, the data will be deposited in the Zenodo repository following appropriate anonymization procedures. The dataset will be accompanied by metadata in Zenodo including: (1) data provenance, (2) patient population characteristics, and (3) a detailed description of the study variables.

Access to data stored in the internal repository for other investigators with legitimate scientific interest will be subject to approval by the Ethics Committee.

This approach ensures compliance with open-access data requirements applicable to publicly funded research projects, while maintaining data within a controlled environment consistent with their nature as personal data.

Data are expected to be available beginning in January 2031, following completion of the study and publication of the primary analysis.

Data will be shared with investigators who provide a methodologically sound research proposal and demonstrate legitimate scientific interest.