Fatigue in Coronary Artery Disease: A Theory of Unpleasant Symptoms-Guided Protocol for a Scoping Review (Preprint)

BACKGROUND Fatigue is a complex and multifactorial symptom that affects 40%–48% of patients with coronary artery disease (CAD), with significant impact on daily functioning, quality of life, and clinical outcomes. Evidence suggests that CAD-related fatigue has unique characteristics, distinct from fatigue in other conditions such as cancer or multiple sclerosis. However, CAD-related fatigue lacks a clear definition, and many instruments were not developed or validated specifically for this population. This conceptual and methodological gap highlights the need to identify definitions, manifestations, influencing factors, consequences, and assessment tools for fatigue in CAD. Nursing theories, particularly the Theory of Unpleasant Symptoms (TOUS), offer a valuable framework to guide this review and strengthen the understanding of CAD-related fatigue. OBJECTIVE The purpose of this scoping review is (1) to map the definitions of fatigue employed in studies specifically involving patients with CAD; (2) to map the manifestations and influencing factors of fatigue, as well as its influence on the performance of CAD-related fatigue; (3) to map and characterize the methods and instruments used to assess fatigue; and (4) to propose a conceptual framework and formulate a definition of CAD-related fatigue. METHODS The scoping review will be conducted following the JBI methodology and in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). A comprehensive three-phase search will be conducted in MEDLINE (Pubmed), CINAHL, Embase, Web of Science, PsycINFO, and Scopus, ProQuest Dissertations & Theses Global and the CAPES Theses and Dissertations Catalog. No restrictions on publication date or language will be applied. Eligible studies will include adults (≥18 years) with a diagnosis of CAD. Screening and selection will be performed by two independent reviewers in Rayyan. Duplicate records will be removed, and any discrepancies will be resolved through discussion, and a third reviewer will be consulted if necessary. Data extraction will be conducted using Covidence, with iterative piloting to ensure consistency. Extracted data will include study characteristics, definitions of fatigue, manifestations, influencing factors, consequences, and assessment of fatigue. A structured categorization and narrative synthesis will be employed, guided by the TOUS. RESULTS A total of 6958 records were identified. After removing 3167 duplicates, 3797 titles and abstracts were screened, remaining 281 full-text articles were assessed for eligibility, and 146 met the inclusion criteria. In addition, four additional studies were included after screening the reference lists. In total, this scoping review included 150 (3.95%) studies that met the predefined inclusion criteria and remained for data extraction. Findings will be presented in tabular and diagrammatic forms, including a conceptual framework and a proposed definition of CAD-related fatigue. CONCLUSIONS This will be the first scoping review to map CAD-related fatigue guided by the TOUS. Its findings will enhance the conceptual clarity of fatigue in CAD, support the development of validated assessment instruments, and inform clinical practice and policy by enabling early recognition and appropriate management of this symptom. Ultimately, this review will provide a foundation for future research and contribute to improving patient outcomes and quality of life. CLINICALTRIAL Open Science Framework (OSF): https://osf.io/geqm6