[Plasticity and remodeling of the myocardium in hypertensive patients. The inotropic effect]

Systolic function of normal hearts is characterised by the sequence isometric-isotonic contraction and dominated by the force-time relationship which, more than the pressure graph, determines myocardial oxygen consumption. It is the main factor of heat production whether or not related to mechanical activity. Apart from the loading conditions, there are two important biological factors during contraction: the structure of the myosin and the quantity of free intracytoplasmic calcium on which the membrane proteins depend. In cardiac hypertrophy, the decrease of Vmax allows the fibre to develop a normal active tension more economically at the expense of its velocity. Depending on the species and tissues, this decrease may be due to a sarcoplasmic and/or a membrane protein modification. The therapeutic inotropic effect is obviously deleterious at fibre level but it may, on the contrary, be economically beneficial from the thermodynamic point of view to the heart as a whole.