The isolated working guinea pig heart: A functional and electrophysiological characterisation

Small animal isolated perfused hearts have been used for over 150 years for the study of cardiac physiology and pharmacology. The guinea pig heart represents the smallest mammalian heart that replicates key features of the human heart - for example, with respect to cardiac action potential duration, ion channel expression, excitation-contraction coupling and intracellular Ca²⁺ handling. In this study we describe the apparatus, instrumentation and characterisation of the isolated working guinea pig heart and utilise state-of-the-art pressure-volume catheters and so forth to characterise systolic and diastolic function in this auxotonically contracting preparation. We describe novel correction formulae to allow rate-dependent variables, such as the QT interval of the ECG and left-ventricular pressure, to be reliably corrected for changes in heart rate.