The development of microconductance technology to study cardiac pressure-volume relations in mice in vivo has significantly advanced the haemodynamic assessment of gene-modified models of cardiovascular disease. In this study, we describe the application of microconductance analysis of cardiac function to the isolated murine ejecting heart. This ex vivo model is complementary to the previously described in vivo preparation, allows assessment without confounding effects of anaesthetic or neurohumoral influences and enables careful control of cardiac loading (particularly preload). Ex vivo pressure-volume relations in the isolated murine heart are sensitive to changes in myocardial contractility induced by beta-adrenoceptor stimulation or beta-adrenoceptor blockade, as well as the effects of chronic pressure overload induced by aortic banding. We present data for both steady-state analyses of the Frank-Starling relation and for assessment of the left ventricular pressure-volume relation over variably loaded beats, which allows investigation of the end-systolic and end-diastolic pressure-volume relations. The measurement of ventricular volume in addition to pressure under carefully controlled loading conditions in the isolated ejecting heart allows a comprehensive analysis of cardiac contractile function, and provides a useful complementary model for the assessment of cardiac performance in murine models of heart disease.
