We report a study of the interactions between epicardial adipose tissue, which is tightly apposed to the heart in vivo, and cardiomyocytes, using rat cells in a novel 3D co-culture system. Our findings are that in addition to being a local source of energy-rich fatty acids which support cardiac function, adipocytes are a source of paracrine factors that modulate the amplitude and rate of contraction. This is achieved by changes in a number of cardiomyocyte signalling pathways