Abstract 9483: Oxidative Stress Induced by Acute Sodium Loading is Associated with Diastolic Dysfunction in Prehypertensives
Introduction: In 'salt-sensitive’ animals, chronic sodium (Na) loading causes oxidative stress and ventricular diastolic dysfunction. In humans, less is known about how early in the course of hypertension these responses begin, or if they differ following acute Na loading.
Hypothesis: Acute Na loading in prehypertensives induces systemic oxidative stress that in turn is associated with post-Na loading ventricular diastolic dysfunction.
Methods: We studied 14 prehypertensive humans (10 male, 4 female; age 28 ± 7 years, blood pressure 132 ± 12/ 77 ± 9 mmHg) over 6 days. Subjects ate a low-Na (20 mMol) diet on days 1-4. On day 5, they received 2 liters of 0.9% saline (308 mMol Na) intravenously over 2 hours, then 130 mMol Na over two high-Na meals. Urinary F-2 isoprostanes from overnight collections were used to measure systemic oxidative stress. Transthoracic echocardiograms were done on day 4 and day 6. Since standard diastolic function measures are less sensitive in structurally normal hearts, we used novel speckle tracking software (EchoInsight, Epsilon Imaging) to obtain a newer measure, global early diastolic strain rate (DSR). We used t-testing and linear regression to evaluate the association between ΔF2-isoprostanes and ΔDSR with Na loading.
Results: F2-isoprostanes increased post-Na loading (4.1 ± 2.1 to 7.3 ± 7.4 pg/mMol Cr, p = .08), as did DSR (0.89 ± 0.20 to 1.08 ± 0.27 s-1, p = .06). However, subjects below the median ΔF2-isoprostanes (group A) had significant increase in DSR post-Na loading; while those above the median ΔF2-isoprostanes (group B) did not (Figure). On linear regression, adjusted for urinary volume excretion, ΔDSR was inversely related to ΔF2-isoprostanes (β -.03, p < .02; r2 = 0.53). In contrast to DSR, other diastolic function measures were unrelated to ΔF2-isoprostanes.
Conclusions: Oxidative stress generated by acute Na loading is associated with impaired diastolic function in prehypertensive humans with structurally normal hearts.
- © 2011 by American Heart Association, Inc.