Myocardial stiffness has been shown to correlate with heart disease, nevertheless, reliable stiffness estimates are hindered by the remarkably complex behaviour and function of the heart muscle. In this work, we use MR-Elastography and rheological experiments to obtain a better understanding of the myocardial material behaviour. MR-Elastography and cyclic shear tests are performed on ex-vivo porcine hearts, under varying frequencies. Our results demonstrate important tissue properties and highlight the viscoelastic properties of the myocardium which are often neglected. Improving our understanding of the interlinked material properties of the heart is a critical step towards the accurate prediction of myocardial stiffness.