Abstract 5853: Renal Excretion of Acute Sodium Load Predicts Diastolic Function Indices in Young Prehypertensives
Background: Chronic high sodium (Na) intake causes ventricular diastolic dysfunction in salt-sensitive animal models and humans. The relationship between renal handling of an acute Na load and diastolic function is not fully defined.
Methods: We studied 11 young (24±5 yrs, 8 male/3 female), non obese, otherwise healthy prehypertensives over 6 days. Subjects ate a 20 mMol Na diet for 4 days. On day 5, they received 2 liters of 0.9% saline (308 mMol Na) over 2 hours, then 130 mMol Na over 2 meals. Urinary Na excretion was measured during saline infusion and continuing until day 6. Echocardiograms were performed the day before and the day after Na loading. We explored changes in early mitral inflow velocity (E), lateral mitral annulus velocity (e′), and E/e′ with t-tests, then identified predictors of change in E/e′ with linear regression.
Results: Subjects had structurally normal hearts with normal systolic and diastolic function by standard indices. E and e′ increased after Na loading (63 to 81 cm/s and 19 to 24 cm/s, both p <.001). Subjects below the median Na excretion rate (6.6 mMol/hr) had similar increases in E (22 vs 14 cm/s, p =.21), less increase in e′ (3 vs 7 cm/s, p = .05), and greater increase in E/e′ (+0.6 vs −0.5, p = .005) when compared to those above the median rate. Upon stepwise regression, the Na excretion rate was the strongest predictor of E/e− change after Na loading (β = −0.2 per mMol Na/hr, p = .001)
Conclusions: Following acute Na loading, young prehypertensives with lower urinary Na excretion rate have poorer diastolic function indices. Differences in renal Na handling could relate both to blood pressure salt-sensitivity and the development of ventricular diastolic dysfunction.