The isolated perfused heart system, as originated by Oscar Langendorff nearly a century ago has become a mainstay of pharmacological and physiological research. The system allows the examination of cardiac inotropic, chronotropic and vascular effects without the complications of an intact animal model. The original design has evolved to encompass both constant pressure and constant flow models in both recirculating and non-recirculating modes, as well as Working Heart mode. The Radnoti perfused heart systems has the capacity to function in any of these configurations, allowing the researcher to have maximal flexibility in experimental design.