Functional evaluation of the rat heart in situ

We have developed methods for evaluating muscle function in the intact rat heart in situ using a contractility index (dP/dt)P-1, calculated from left ventricular pressure derivative-left ventricular pressure loop plots. Aortic flow measurements were also taken to further characterize in situ rat heart function. The preparation remained functionally stable and was within physiological blood gas and pH limits for at least 30 min following surgical procedures. The contractility index was not influenced by increased afterload, decreased preload or increased heart rate; however, appropriate changes were observed following isoproterenol and propranolol administration. Appropriate changes in aortic flow measurements were observed also with the above interventions. These studies demonstrate that the in situ rat heart is a stable physiological experimental preparation. It should be useful for evaluating heart function since a contractility index derived from pressure-velocity relationships and measurements necessary for pump function analysis can be obtained simultaneously.