The biological limits of cardiac adaptation to chronic overload

Cardiac hypertrophy, which occurs during chronic mechanical overload, is one of the numerous examples of biological adaptation to environmental requirements. As such, it is achieved at random by trial and error, and adaptation represents the sum of various modifications in gene expression, including the shift in isomyosin or in iso Na+/K+ ATPase; the decrease in beta-adrenergic and muscarinic receptors or in SR Ca2+ ATPase densities and the unchanged density in Ca2+ current. Some of these changes are beneficial at the cellular level but finally detrimental for the organism as a whole, as is the slowing of Vmax. There are also detrimental modifications, such as hypertensive macroangiopathy, the slowing of relaxation and changes in stiffness. These various modifications may provide a new key for future pharmaceutical research.