Salt and left ventricular hypertrophy: what are the links?

Left ventricular hypertrophy is a frequent and prognostically unfavourable finding in patients with essential hypertension and has been found to be a predictor for the development of essential hypertension in normotensive subjects. Among various genetic, haemodynamic and humoral determinants, dietary salt intake has been demonstrated to influence left ventricular mass in hypertensive disease. Several cross-sectional studies have shown a close relation between dietary salt intake and parameters of left ventricular hypertrophy. Moreover, reduction of dietary sodium intake was associated with a decrease of left ventricular mass in a prospective study. The underlying mechanism of how salt intake modulates myocardial structure has not been explained yet. Three possible explanations are discussed: (1) sodium influences left ventricular mass via raised preload, (2) the sympathetic nervous system acts as a mediator, and (3) the renin-angiotensin-aldosterone system is the responsible link. Recent animal experiments and clinical studies suggest that the renin-angiotensin-aldosterone system may mediate both the cardiotrophic and the blood pressure raising effects of salt. However, not all individuals have a similar high susceptibility to blood pressure elevation develop left ventricular hypertrophy when exposed to high salt intake. We suggest that the underlying mechanism is a dysregulation of the renin-angiotensin-aldosterone system. Some individuals may have an impaired downregulation of angiotensin II synthesis when challenged with high salt intake. Accordingly, we found that relatively too high levels of angiotensin II in relation to urinary sodium excretion were associated with left ventricular hypertrophy in these individuals on high salt intake.