[Left ventricular hypertrophy. Advantages and drawbacks].

Abstract

The increase of the muscular mass of the left ventricle represents, for the ventricular pump, a mechanism of adaptation to a normal process (growth, sport, etc.) or a pathological process (mechanical overload or cardiomyopathy). The geometrical variations which are associated, tend to normalize the performances and/or the systolic constraints, determining elements of the metabolic needs of the myocardium. If left ventricular hypertrophy is not quantitatively, geometrically and functionally adequate and if the contractility and precharge reserves become exhausted, the systolic performance of the ventricular pump is altered and becomes extremely dependent upon the systolic constraints which are then increased. It may be difficult to take into consideration an insufficiency of the contractility of the ventricular muscle in front of clinical signs of cardiac insufficiency which is conditioned by abnormalities in the filling of the ventricular pump. In addition, some "pathological" hyperthophies may secondarily induce an alteration of the intrinsic properties of the muscle (during its contraction, relaxation an/or extension), susceptible to induce or aggravate a ventricular insufficiency. The causes remain uncertain, since a metabolic imbalance of the myocardium by increase of the needs as well as a decrease of the coronary reserve and the exchange capabilities are commonly accepted. What are the mediators of these mechanisms of quantitative, geometric adaptation and also--at least in some animals--structural adaptation (isoenzymes of myosin)? Why do they seem, at times, strangely absent or quickly out-of-date, or sometimes excessive, with all the drawbacks specific to hypertrophy? The answer to these questions would perhaps represent a new therapeutic approach to left ventricular insufficiency.