Techniques for isolation and performance of the perfused guinea pig working heart

This study demonstrated new approaches which enabled evaluating the work performance in both ventricles of an isolated guinea pig heart. By changing the right atrial filling pressure (RAFP, preload) from 6 to 20 mm of Hg at a constant aortic pressure (Pa, 20 mm of Hg), cardiac output, stroke volume, aortic flow, coronary flow, cardiac work, O2 consumption, CO2 output, as well as end-diastolic ventricular, and pulmonary arterial pressures increased. Cardiac contractility and both ventricular systolic pressures reached peak values between 12 and 14 mm of Hg of RAFP and then gradually decreased. With graded increases of Pa (afterload) from 10 to 45 mm of Hg at a fixed RAFP (8 mm of Hg), coronary flow, cardiac contractility, cardiac work, cardiac O2 consumption, glucose utilization rate, and pulmonary arterial and both ventricular systolic pressures increased. Although aortic flow decreased with an increase in Pa, cardiac output, stroke volume, and coronary resistance did not show significant changes. Furthermore, cardiac mechanical efficiency decreased with an increase of pre- or afterload of the perfused isolated heart. These findings indicate that the total working heart model is suitable for studying cardiac functions.