A MICROCOMPUTER SYSTEM FOR HEMODYNAMIC MEASUREMENTS IN ISOLATED, WORKING RAT HEARTS

This study describes the application of an Apple IIe microcomputer in combination with a pre-processor in the on-line calculation of haemodynamic variables of the isolated working rat heart and of relative rapid chnges in these variables, induced by variations in left atrial filling pressure (preload) and end-diastolic aortic pressure (afterload). Variables such as heart rat, systolic and diastolic left ventricular pressure, the maximal positive and negative first derivative of the left ventricular pressure, systolic and diastolic aortic pressure and aortic flow were continuously calculated and printed at minimal intervals of 6 s. A newly designed procedure to detect the activation of the electrogram, which was necessary to start the detection of a new cardiac cycle, is described.