The inZHerz initiative, funded by the German Federal Ministry of Education and Research (BMBF) under grant number 13GW0278A, ran from 1 December 2018 to 31 December 2022. The project was led by Oliver Rehermann of Biotronik Vertrieb GmbH & Co. KG, which served as the sole partner and responsible organization. The primary aim was to enhance the early detection of life‑threatening arrhythmias by integrating individual circadian cardiopulmonary rhythm analysis into a comprehensive digital care network. The project’s scientific thrust focused on three interrelated domains: prevention and early detection, telemonitoring, and risk ranking with knowledge transfer to broader patient groups.

Central to the technical outcome was the development of a structured care concept that remained largely unchanged throughout the project. This concept guided the creation of detailed standard operating procedures (SOPs) that initially addressed rhythm events exclusively, with the possibility of expanding to other parameters after project completion. The SOPs were designed to be actionable by clinicians and technicians, incorporating steps such as trend analysis of atrial arrhythmias, electrode performance checks, bradycardia/CRT monitoring, ICD programming verification, home‑monitoring settings review, medication assessment, and patient contact or referral when necessary. A representative SOP for atrial arrhythmia evaluation was documented, outlining a sequence of eight checks and corresponding interventions ranging from no action to ICD reprogramming or medication adjustment. These SOPs were integrated into workflow diagrams that illustrated patient enrollment into the arrhythmia care program and the flow of data from implantable cardioverter‑defibrillators (ICDs), through a telemedicine infrastructure, to a central case file.

The project also established a robust data handling framework that addressed user management and role‑based access while ensuring compliance with data protection regulations. “Red card” rules were defined to trigger mandatory interventions for device defects or potentially life‑threatening events, with documentation of the response. Medication data were incorporated into risk calculations to improve accuracy. Long‑term Holter‑ECG screening was enabled through personalized ECG patches that patients could apply themselves, or via mobile services that applied patches during routine visits. The patches transmitted data to a mobile service, which forwarded it to the central monitoring unit (TMZ). The TMZ applied a circadian algorithm to assess patient risk, generating analysis reports and, when appropriate, clinical recommendations that were shared with the treating medical facility and the patient, sometimes accompanied by specific guidance for patients and relatives.

A key scientific insight of the project was the recognition that heart‑rate dynamics preceding life‑threatening arrhythmias follow a circadian pattern. Unlike previous studies that averaged data across all time points, the inZHerz approach preserved individual rhythms, revealing that nocturnal heart‑rate increases were absent before arrhythmias, whereas such increases appeared 10 minutes before evening events and up to an hour before morning events. This temporal differentiation suggested distinct pathophysiological mechanisms at different times of day and underscored the value of circadian‑aware prediction models.

The project’s outputs include a validated digital platform that can be deployed in primary care settings, particularly in rural areas where specialist shortages exist. By automating risk assessment and alerting clinicians to critical changes, the system aims to reduce the incidence of sudden cardiac death, which currently claims over 65,000 lives annually in Germany, and to lower associated healthcare costs. The inZHerz project therefore delivers both a scientifically robust methodology for arrhythmia prediction and a practical, scalable solution for high‑risk patient management.