[The left ventricle at different stages of a two steps mechanical overloading. Electron microscopic study in the rat...

The left ventricle myocardium of rats subjected to a two steps mechanical overloading (abdominal aorta constriction + aortic insufficiency) was examined in the light and electron microscopes at several stages of the load, and particularly after 3 to 6 months when the animals exhibited congestive heart failure. In these conditions, the heart weight exceeded the control by more than 100 %. In the later stages, the absence of parallelism between heart weight and cell diameter was compatible with a process of hyperplasia. Cellular lesions looking like recent were found more and more frequently with time. Within apparently normal cells proliferation of small mitochondria, nucleoli and Golgi apparatus are compatible with some deficit in energy balance, which is usually encountered only in early stages of the load.