Abstract
BACKGROUND: Delivering evidence-based stroke rehabilitation in clinical practice is challenging due to intervention complexity and healthcare system factors. The Comprehensive High-dose Aphasia Treatment (CHAT) program incorporates best-practice principles for aphasia rehabilitation, but uptake within healthcare services is limited. A multifaceted implementation strategy was developed to support CHAT delivery as part of a single-site 3-year pre-post hybrid type II implementation-effectiveness study. This process evaluation sought to determine the influence of the implementation strategy and organisational context, and to identify mechanisms of impact on the outcomes of the complex intervention. METHODS: A longitudinal mixed methods process evaluation was conducted over three years, with data collected at 3-6-month intervals to capture process and organisational changes. Data were collected through clinician interviews and focus groups, behaviour-change surveys, training logs, observational checklists, and questionnaires. Qualitative data was analysed using the Framework Method, then triangulated with quantitative and observational data, informed by the Medical Research Council (MRC) Process Evaluation Framework for Complex Interventions. A logic model was developed to support conceptual linkage of the complex interrelationships among factors impacting implementation success. RESULTS: Twenty-four clinicians participated, and CHAT was delivered to 67 participants with aphasia. All implementation strategy components were delivered as intended, and CHAT was successfully implemented. Many contextual barriers identified in the first year were addressed as processes were streamlined, mediated by organisational responsiveness and commitment, including allocation of clinical positions. Key mechanisms of ‘cognitive overload and clinician fatigue’ were counteracted by clinicians’ sense of ‘professional recognition and pride’ at being involved in the program, and their ‘immersion in CHAT as part of a team’. Implementation support needs decreased over time and sustainment plans were highlighted. CONCLUSION: This study highlights benefits of evaluating implementation processes over time to understand how adaptions occur in response to challenges, and the importance of organisational and leadership commitment. Though implementation was challenging, processes to mitigate barriers and support clinicians led to positive implementation outcomes. Our findings show the potential for complex interventions to be sustainably embedded within clinical services, providing key considerations to inform future implementation of intensive aphasia services and contributing to global efforts to improve rehabilitation services. CLINICAL TRIAL NUMBER: Not applicable. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12913-026-14329-0.