High-sodium diet does not worsen endothelial function in female patients with postural tachycardia syndrome

Abstract

Purpose: Postural tachycardia syndrome (POTS), a syndrome characterized by orthostatic symptoms and a heart rate increase of at least 30 beats per minute in the absence of hypotension upon standing, is often accompanied by increased sympathetic activity and low blood volume. A common non-pharmacologic recommendation for patients with POTS is a high-sodium (HS) diet with the goal of bolstering circulating blood volume. The objective of this study is to assess the effects of 6 days of a HS diet on endothelial function in POTS.

Methods: A total of 14 patients with POTS and 13 age-matched healthy controls, all females, were studied following 6 days on a low-sodium (LS) diet (10 mEq/day) and 6 days on a HS diet (300 mEq/day) in a crossover design. We measured endothelial function following reactive hyperemia in the brachial artery using flow-mediated dilation (FMD), leg blood flow (LBF) using strain gauge plethysmography in the calf, and reactive hyperemic index (RHI) in the microcirculation of the hand using pulsatile arterial tonometry.

Results: On the LS diet, FMD% did not differ between patients with POTS and the healthy controls although peak brachial artery diameter was lower for the patient group. RHI was higher for the patient group than for the controls, but there were no differences in post-ischemic LBF increase. On the HS diet, there were no between-group differences in FMD%, LBF increase, or RHI.

Conclusion: In summary, a HS diet for 6 days did not induce endothelial dysfunction. This non-pharmacologic treatment used for patients with POTS does not negatively affect endothelial function when used for a sub-acute duration.

Trial registration: ClinicalTrials.gov NCT01550315; March 9, 2012.

Keywords: Autonomic nervous system; Dietary salt; Endothelial function; Nitric oxide; Postural tachycardia syndrome.

Figure 1.. Effect of Low- and High-Sodium Diets on Endothelial Function

Percent change in Flow Mediated Dilation (FMD, %; Panel a), Leg Blood Flow (% LBF / min; Panel b) and Reactive Hyperemia Index (RHI; Panel c) on Low Sodium (LS) and High Sodium (HS) diets for POTS and controls (HC). Values are expressed as means with error bars indicating the SEM. Differences between diets were assessed using Mann Whitney Rank-Sum and differences between groups were assessed using Wilcoxon Sign-rank.* P < 0.01 for difference between POTS and controls on the LS diet.