Mixed-methods process evaluation of the “Karl-Heinz” cardiac prehabilitation program in older patients: protocol for the PRECOVERY trial

BACKGROUND: Structured cardiac prehabilitation programs for older patients prior to cardiac procedures address an unmet medical need, yet implementation evidence remains scarce. "Karl-Heinz" (Kognitiv & kardiale Prehabilitation vor Herzinterventionen; cognitive and cardiac prehabilitation prior to cardiac procedures) is a tailored prehabilitation program designed to improve quality of life and reduce mortality 12 months after elective cardiac procedures. PRECOVERY is a randomized, controlled, two-arm parallel group, assessor-blinded, multicenter trial evaluating its clinical efficacy. This study protocol outlines the embedded mixed-methods process evaluation examining both the delivery and implementation of "Karl-Heinz." The objectives are (1) to examine the implementation process across prehabilitation centers, including contextual barriers and facilitators; (2) to assess the intervention's fidelity, dose, adaptations, reach, and the quality of health professional training; and (3) to analyze key stakeholders' perspectives on implementation and perceived impact. METHODS: The quantitative strand will collect standardized questionnaires from trial participants (n = 422, aged ≥ 65 years), their relatives, and health professionals from participating prehabilitation centers. Additional data sources include therapy plans and patient diaries. Furthermore, we will systematically analyze evaluation data from health professionals delivering the intervention to assess training delivery. The data will be analyzed using the "joint frailty model for longitudinal data and terminal event", supplemented by exploratory analyses of main trial data. The qualitative strand will include semi-structured interviews with a subsample of patients (n = 24) and relatives (n = 24) before and after the cardiac procedure. We will interview physicians performing the cardiac procedure (n = 9) and conduct focus groups (three with health professionals involved in prehabilitation delivery, two with general practitioners of prehabilitated patients). Qualitative data will be analyzed using structured qualitative content analysis. The results from both strands will be triangulated and related to the results from the main trial. DISCUSSION: This process evaluation will provide detailed insights into the implementation and perceived impact of "Karl-Heinz." Capturing perspectives from multiple stakeholder groups along with a detailed analysis of training processes will help to identify contextual factors, facilitators, barriers, and deviations. The mixed-methods approach will enable a thorough understanding, support the intervention's refinement, optimize allocation of resources, overall reproducibility, and the assessment of possible integration into routine care. TRIAL REGISTRATION: German Clinical Trials Register (DRKS; http://www.drks.de ; DRKS00030526). Registered on 30 January 2023.