Development and reversal of pressure-induced cardiac hypertrophy. Light and electron microscopic study in the rat under temporary aortic constriction.

Light and electron microscopy, combined with morphometry, were utilized to study myocardial cell modifications induced by a temporary abdominal aortic constriction in the rat. During the early stage of active hypertrophy, cell enlargement in the subendocardial layers of the left ventricle was predominant. This enlargement may be partly due to intracellular edema, characteristic of cell damage. Degenerative foci leading to fibrous scars were found primarily in the subendocardium and midwall layers. The times taken by the different cell structures to adapt to modifications of the load were rather different; some adapted very rapidly (nucleoli, intercalated discs), while others were much slower (cell diameter, mitochondria).