Some Properties of the Mammalian Ventricular Muscle

AbstractSome properties of ventricular muscle were studied in perfused dog's hearts. Two methods were employed. With the first, the « tension » method, the ventricles acted as a single muscular mass. This method allowed the study of isometric, isotonic and after-loaded contractions. The « pressure » method was applicable only to record the pressure changes in the right ventricle during isometric contractions at different diastolic volumes.The tension-« length » diagrams of the resting and isotonically or isometrically contracted ventricle resemble those of striated muscles (fig. 2). The diagram obtained with isotonic contractions differs from that found with isometric responses.The pressure-volume diagram of the resting ventricle indicates the the capacity of the unstretched right ventricle of the dog is about 30 cc. (figs. 4 and 5).The amplitude of both the isotonic and the isometric contractions increases with the initial length or volume over a wide range (figs. 3 and 6); the work performed in the isot...