[Left ventricular insufficiency: definitions and mechanisms].

Left ventricular failure is defined as an inability to maintain, under resting conditions, a cardiac output sufficient for the oxygen requirement. It is accompanied by a rise in trans-mural ventricular filling pressure and/or a reduction in systolic volume. It may be linked to an alteration in the systolic performance and/or an alteration in the characteristics of the left ventricle. The compensatory mechanisms are represented by the noradrenergic stimulation; a rise in the muscular mass of the left ventricle and the associated changes in its geometry the heterometric regulation of Frank Starling. Some peripheral adaptive mechanisms such as salt and water retention, arteriolar vaso-constriction and a rise in the peripheral extraction of oxygen contribute to compensating for the lower systemic cardiac output.