Contractile State of Cardiac Muscle Obtained from Cats with Experimentally Produced Ventricular Hypertrophy and Heart Failure

The contractile state of papillary muscles from hypertrophied and from failing right ventricles of cats with pulmonary artery constriction was studied. In muscles from failing hearts, the maximum velocity of shortening, active length-tension curves, and maximum rate of tension development were decreased, while the passive length-tension curves and the time from stimulation to peak tension were normal. The augmentation of isometric tension achieved by paired electrical stimulation, increasing frequency of contraction, and strophanthidin was reduced. In muscle from hearts without failure but with ventricular hypertrophy, there were qualitatively similar depressions of contractile function, although of lesser magnitude. It is concluded that congestive heart failure is associated with extreme quantitative abnormalities of the intrinsic contractile state of each unit of heart muscle, which reflect a depression in the intensity of the active state. Further, ventricular hypertrophy in the absence of failure is associated with a depression of the contractility of each unit of myocardium, while cardiac compensation is maintained by the increase in muscle mass.