Ultrastructural aspects of contractile proteins in cardiac hypertrophy and failure.

A review is presented in this chapter of morphological changes in contractile elements of cardiac muscle cells in hypertrophy and failure, with emphasis on alterations occurring in human hearts in the late stages of hypertrophy. The formation of new sarcomeres involves the synthesis of a variety of different proteins, their aggregation into filaments, and the organization of filaments into specific tridimensional arrays. Z-line material appears to play an organizer role in the formation of new sarcomeres. The ultrastructural appearance of contractile elements in hypertrophied muscle cells varies according to the cause and the stage of the hypertrophy. Myofibrillar lysis, with preferential loss of thick myofilaments, occurs in the late stages of hypertrophy in association with degenerative changes, including dissociation of intercellular junctions, proliferation of sarcoplasmic reticulum, cellular atrophy, and interstitial fibrosis.