Cardiovascular diseases remain the leading cause of mortality worldwide and their global burden is increasing. Over the last few decades, progress in cardiovascular research has been significantly hindered by a lack of appropriate research models. The vast majority of research is currently conducted using isolated cell preparations or in vivo animal studies. However, the data collected using current in vitro approaches is often oversimplified and this makes the translation of results from the laboratory to clinical trials challenging. Additionally, cardiac tissue undergoes a rapid remodelling when removed from the body, which has limited in vitro studies to acute time points. To date, there are no cardiovascular models that can be cultured without significant changes in cardiac structure and function. These factors have significantly hampered translational cardiac research and the development of novel therapeutics for cardiovascular diseases; it is imperative that this issue is addressed. What is required is a model that bridges the gap between in vitro and in vivo studies and that can be maintained in a physiological state for prolonged periods in culture. Myocardial slices are 100- to 400-μm-thick slices of living adult ventricular myocardium, prepared using a high-precision vibratome. They retain the multicellularity, complex architecture and physiology of adult cardiac tissue, and their thinness allows the diffusion of oxygen and other metabolic substrates into their innermost cells, maintaining viability in the absence of coronary perfusion in vitro (Nature Protocols,2017). Additionally, as multiple slices can be produced from a single specimen, throughput can be increased and the number of animals used can be reduced. We hypothesised that recreating the physiological in vivo cardiac environment was fundamental to maintain the structure and function of myocardial slices and prevent the remodelling that occurs in culture. By applying electromechanical stimulation and physiological preload to myocardial slices for prolonged periods we showed that numerous cardiac structural, functional and transcriptional properties are optimally maintained at a specific preload (sarcomere length (SL)=2.2μm) and this allowed us to culture myocardial slices generated from a preclinical animal model (rabbit) for 5 days without a loss of contractile function. When cultured at other SLs, to simulate cardiac unload and overload (SL=1.8, 2 or 2.4μm), slices displayed adaptive responses without changes in viability. Finally we have demonstrated that this platform can be applied to maintain human heart failure myocardial slices in vitro, making it particularly useful for translational and regenerative medicine research. This is the first approach that can successfully maintain adult cardiac tissue in a physiological state in vitro.