Functional morphology of the pressure- and the volume-hypertrophied rat heart.

We studied hearts in which hypertrophy was caused by both pressure and volume overload. Pressure hypertrophy was induced by an aortic constriction; volume hypertrophy was induced by an iron-copper deficiency (anemia). The ventricular weight was increased by 34% in the pressure-hypertrophied hearts at the end of 6 weeks. The ventricular weight was increased by 54% in the volume-hypertrophied hearts at the end of 3 months. A potassium arrest-formalin fixation technique was used to produce a "diastole-like" ventricle. In the pressure-hypertrophied ventricle, the ventricular wall thickness and external radii were significantly increased, whereas the valve-to-apex distance and internal radii remained unchanged. We also found that in the volume-hypertrophied ventricle there was an increase in the valve-to-apex distance, external radii, internal radii, and wall thickness. Although external and internal dimensions increased, the ventricular shape did not change significantly in the volume-hypertrophied ventricle.