A high sodium diet can reduce the accelerated heart rate and other distressing symptoms experienced by patients with postural tachycardia syndrome on standing, new research suggests.
In the small study of almost 30 female patients, researchers found POTS patients on the high sodium diet had a statistically significant reduction in upright heart rate (median 117 beats/min) compared to POTS patients on the low sodium diet (129 beats/min), though still above the range of healthy controls (85 to 96).
In POTS patients on the high sodium diet, they also had significantly less of a change in heart rate when moving from supine to upright compared with those on the low sodium diet (46 beats/min compared to 60 beats/min). Healthy control heart rates increased by an average of 23 beats. While the intervention didn’t “normalise” patient responses, experts say the findings are important given the lack of established treatments.
POTS is defined by an orthostatic heart rate increase of at least 30 beats/min in the absence of orthostatic hypotension.
Despite major bodies including the Canadian Cardiovascular Society recommending a high sodium diet for POTS, the US authors noted this was the first study to test whether such a diet lessened orthostatic tachycardia.
In the study published in the Journal of the American College of Cardiology, researchers compared postural heart rate and other markers of POTS such as plasma norepinephrine and blood volumes of 14 POTS patients and 13 healthy controls after consuming a low (10mEq sodium/day) or high sodium (300mEq sodium/day) diet for six days.
In addition to the effect on heart rate, standing norepinephrine levels dropped significantly with the high sodium diet, and both total blood volume and plasma volume increased.
There was a nonsignificant trend for lower symptom burden among those POTS patients on the high sodium diet. Symptoms associated with POTS patients include palpitations, light-headedness, mental confusion, blurred vision, shortness of breath, tremulousness, chest discomfort, headache and nausea.
“The deficit in plasma volume evident in previous studies and in the low sodium phase of this study was eliminated by an high sodium diet, suggesting that the restoration of plasma volume contributed to improvement, although not normalisation, in POTS,” the authors wrote.
The findings provided “solid evidence” in support of a high sodium diet, they said.
POTS prevalence estimates in the US range from 0.2 to 1.0%
Australian cardiologist Dr Yusuke Sata, who leads the Alfred Hospital’s hypertension clinic, told TMR he received between five and 10 new patient referrals each month.
“Despite the large number of patients suffering from this condition, there are no well-established pharmacological or non-pharmacological treatments,” said Dr Sata, also a researcher at the Baker Heart and Diabetes Institute.
Patients often present with tachycardia, dizziness and light-headedness, he said.
“The triggers of these symptoms are various and sometimes overlapping with anxiety. I believe a patient with tachycardia should be investigated appropriately – using a Holter monitor, blood tests etc. – and should be referred to a cardiologist if it is an ongoing issue.”
Although the high sodium patients still met POTS criteria, Dr Sata said the results supported trialling the diet before pharmacological approaches, especially in less severe cases.
“Additional intervention might be warranted on top of non-pharmacological diet therapy. Perhaps combination therapy of high sodium diet and medication would benefit most POTS patients, particularly those with severe and treatment-resistant [symptoms].”
The short study timeframe was a drawback given POTS is often a chronic condition, but caution was warranted for long-term use given the lack of research and the possibility of sustained hypertension, he added.