Studies have demonstrated that POTS patients have a decreased volume of plasma and high serum norepinephrine levels that occur with standing. It would be reasonable to assume, therefore, that increasing oral sodium intake would have a salutary effect on the physiologic derangements that occur in POTS.
In a recent study, researchers have found evidence on the effect of a high sodium diet in POTS. They reported that a high-sodium diet could cause a smaller increase in heart rate and lower norepinephrine level, plasma renin activity (PRA), and aldosterone level while upright. A very high sodium load (6.9 g) over 5 full days improves the parameters associated with postural orthostatic tachycardia syndrome (POTS) researchers found.
The study findings were published in the Journal of the American College of Cardiology on April 26, 2021.
High sodium intake is recommended for the treatment of postural tachycardia syndrome (POTS) to counteract hypovolemia and elevated plasma norepinephrine that contributes to excessive orthostatic tachycardia but, evidence of its efficacy is not available. Therefore, Dr Emily M. Garland and her team conducted a study to test whether a high sodium (HS) diet reduces orthostatic tachycardia (Δ heart rate) and upright heart rate compared with low sodium (LS) diet in POTS patients and further assessed its effect on plasma volume (PV) and plasma norepinephrine.
In this crossover study, researchers included a total of 27 participants, among which 14 were POTS patients and 13 were healthy control subjects (HC). They received LS (10 mEq sodium/day) or HS (300 mEq sodium/day) diet for 6 days. The researchers measured the supine and standing heart rate, blood pressure, serum aldosterone, plasma renin activity, blood volume, and plasma norepinephrine and epinephrine.
Key findings of the study were:
Upon analysis, the researchers found that the HS diet reduced upright heart rate and Δ heart rate compared with the LS diet in POTS patients.
They also found that total blood volume and PV increased, and standing norepinephrine decreased with the HS compared with the LS diet.
However, they noted that compared with healthy controls, patients with POTS had higher upright heart rates, greater change in heart rate (from supine to standing), and higher upright plasma norepinephrine, despite no statistically significant difference in overall plasma volume.
The authors concluded, "In POTS patients, high dietary sodium intake compared with low dietary sodium intake increases plasma volume, lowers standing plasma norepinephrine, and decreases Δ heart rate."
For further information:
https://www.jacc.org/doi/10.1016/j.jacc.2021.03.005