The potential of programme theory in bridging the evidence into practice gap in implementation science: a worked example of integrating palliative care into heart failure management.

Implementation science has been defined as the scientific study of methods focused on promoting the systematic uptake of research findings into routine practice in order to improve the quality and effectiveness of healthcare services. However, a recent critique of the science has highlighted a research to practice gap paradox suggesting that rather than closing the gap, implementation science may be reinventing it. Others have more recently provided a further critique focusing on the promises and pitfalls of implementation science, arguing that the field needs to further develop and grow. Our paper aims to contribute to this call by suggesting one possible way forward. To do this we first explore the ideas and assumptions underpinning implementation science, before we introduce the benefits of realist approaches - which are increasingly recognised as crucial for addressing the research to practice gap paradox as they deal with real world complexity. Whilst realist approaches may help move the field of implementation science forward, we also point out that the theories within this field can also help to improve understanding in realist research. In summary, our paper challenges the growing reliance on implementation theories, models and frameworks as the only starting point for research in this field, and we argue that realist programme theory may be equally useful.