Patients with heart failure undergoing cardiac surgery face a significantly increased perioperative risk, yet no standardized strategy exists to mitigate this risk effectively. Current preoperative management relies on optimization of medical therapy without a structured prehabilitation approach. Given the strong association between eleveated preoperative N-terminal pro-B-type natriuretic peptide levels and postoperative outcomes, patients at increased risk could be identified using this biomarker. Telemedical disease management programs have demonstrated efficacy in outpatient heart failure care, but their role in preoperative optimization remains underexplored. This study aims to assess whether a structured, multidisciplinary, telemedicine-assisted prehabilitation program can reduce perioperative complications, and improve surgical outcomes.

Patients with heart failure undergoing elective cardiac surgery represent a particularly vulnerable population with a substantially increased risk of perioperative morbidity and mortality. Despite advances in surgical techniques and perioperative care, adverse outcomes such as early postoperative mortality, need for extracorporeal membrane oxygenation (ECMO)need for temporary renal replacement therapy, , and prolonged intensive care unit (ICU) stay,remain frequent in this high-risk group. Current perioperative management largely relies on outpatient treating physicians to optimize guideline-directed medical therapy (GDMT) without a structured, standardized strategy for preoperative optimization or "prehabilitation" tailored to heart failure patients. A key issue for resource intensive optimization programs is the need for good patient selection to identify high-risk patients. N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a well-established biomarker reflecting cardiac wall stress and neurohormonal activation. Elevated NT-proBNP levels are independently associated with adverse perioperative and long-term outcomes in patients undergoing both non-cardiac and cardiac surgery. Retrospective data from large surgical cohorts, including analyses from our center, have demonstrated that high preoperative NT-proBNP levels are linked to increased ICU length of stay, higher rates of renal replacement therapy and ECMO use, as well as increased short- and long-term mortality. Importantly, an improvement in measured NT-proBNP levels,reflecting improved heart failure status, were associated with significantly better perioperative outcomes, suggesting that NT-proBNP is not only a risk marker but also identifies potentially optimizable patients. Telemedical disease management programs have proven effective in outpatient heart failure care by improving adherence to GDMT, enabling early detection of clinical deterioration, and reducing hospitalizations. However, the application of such structured telemedicine-assisted interventions in the preoperative setting of cardiac surgery has not been systematically evaluated. The perioperative period offers a unique therapeutic window in which optimization of volume status, neurohormonal blockade, functional capacity, and patient education may translate into improved surgical readiness and outcomes. The PREPARE-HF project was designed to address this unmet clinical need by evaluating a multidisciplinary, telemedicine-assisted preoperative optimization program for high-risk heart failure patients scheduled for elective cardiac surgery. The intervention integrates structured heart failure education, optimization of guideline-directed medical therapy, continuous telemonitoring, supervised exercise training, and psychological support, with the aim of improving perioperative complications compared with standard of care. PREPARE-HF is conducted as a prospective, randomized, open-label ontrolled clinical trial in which 162 patients with elevated NT-proBNP levels (≥1500 ng/L) are randomized in a 1:1 ratio to either the intervention program or standard preoperative care, with stratification according to surgical procedure type. The primary endpoint is a hierarchical composite outcome assessed using the Finkelstein-Schoenfeld win ratio methodology, incorporating all-cause mortality, need for extracorporeal membrane oxygenation, requirement for renal replacement therapy, and length of intensive care unit stay within 30 days after surgery. Secondary endpoints include safety endpoints, preoperative events, perioperative complications, short- and long-term mortality, functional capacity, quality of life, biomarker dynamics, and adherence to guideline-directed heart failure therapy, enabling a comprehensive assessment of the intervention's impact on perioperative and long-term outcomes in this vulnerable patient population.

Inclusion Criteria:

• Indication for elective cardiac surgery in the Heart team
• NTproBNP ≥ 1500 ng/L
• ≥ 18 years willing to participate in trial
• Written informed consent

Exclusion Criteria:

• Neuropsychiatric disorders / illnesses (e.g. drug addiction, alcohol abuse) that do not allow adherent participation in the study
• No sufficient ability to measure and transfer data or existing support in the social environment
• no sufficient ability to communicate (language skills, eyesight, hearing)
• Pregnancy
• Chronic kidney disease requiring dialysis
• Planed procedure: heart transplantation (HTX), implant of left ventricular mechanical assist devices (L-VAD)

following publication of primary and secondary results

Data will be shared upon reasonable request.

Blinding is not feasible because the intervention involves overt telemedical monitoring, patient education, and individualized therapeutic adjustments that are readily apparent to both patients and healthcare providers, necessitating an open-label study design.