Abstract 13142: Effects of Subacute and Acute Salt Loading on Diastolic Function in Young Normotensive Individuals
Introduction Chronic excess salt intake may have blood pressure-independent adverse effects on the heart with myocardial hypertrophy and fibrosis. Subacute salt loading has been reported to impair left ventricular (LV) diastolic function in hypertensive individuals. However, results about effects of dietary sodium on diastolic function in normotensive individuals have been conflicting and the mechanisms are poorly understood.HypothesisWe assessed the hypothesis that dietary sodium affects diastolic function in normotensive subjects by altering preload and intrinsic myocardial relaxation properties.
Methods Ten healthy normotensive subjects (age 24.8 ± 3.6 years) entered a 2-week crossover study with 1-week of low sodium (LS) diet <10 mEq/day and 1-week of high sodium (HS) diet >200 mEq/day. At the end of each study week, LV dimensions, systolic and diastolic function were measured with echocardiography before and after 2L of normal saline bolus infusion.ResultsSaline infusion led to similar increase in stroke volume and cardiac output after both HS and LS diet, and there was no change in blood pressure or heart rate (Table). The early myocardial relaxation velocity E’ at lateral annulus was higher at baseline after HS diet than LS diet (15.9 ± 2.4 vs 14.8 ± 1.7 cm/s; p = 0.01). There was no significant change in E’ with saline infusion after HS diet, but a significant increase after LS diet (-1.1 ± 4.3 vs 10.2 ± 10.4%; p = 0.04). The E’ at septal annulus showed similar response to dietary sodium and saline infusion.
Conclusions In young normotensive subjects, dietary sodium intake is associated with higher E’ at baseline but a blunted increase of E’ in response to volume loading. These findings suggest that a short course of high sodium intake may have both increased preload and decreased myocardial relaxation response. Further research should be undertaken to discern preload effects and study the influence of more chronic change in dietary sodium on diastolic function.
- © 2011 by American Heart Association, Inc.