One of the most prominent and debilitating features of POTS is a very marked increase in heart rate upon adopting an upright posture. This causes the patient to experience very fast heart palpitations which are both scary and very uncomfortable. The patient therefore will try and sit down or lie down to feel better but this is at the cost of becoming increasingly deconditioned in the medium and long term.
In the overwhelming majority of patients, this excessive rise in heart rate is explained by an exaggerated release of ‘flight or fight’ hormones such as adrenaline and noradrenaline. Why this happens we don’t understand but if we can in some way blunt the increase in heart rate then there is a likelihood that we can potentially improve the ability of the patient to stand for longer with less symptoms.
We already have some medications which can help with this such as beta-blockers and Ivabradine and in those patients who can tolerate them, this strategy of reducing the heart rate does result in some symptom improvement. It is worth noting however that for some reason POTS patients tend to be particularly prone to side effects and many of them simply don’t tolerate the commonly used medications. We, as POTS doctors, are therefore always on the lookout for any other medications which can help reduce the heart rate and why may possibly be better tolerated by patients. This is where the medication I am going to talk about today comes into the discussion.
Melatonin is an endogenous compound which is secreted by our pineal gland and is involved in regulating the circadian rhythm and acts as a signal for darkness. It is both a hypnotic and chronobiotic (an agent that can cause phase adjustment of a disrupted body clock)
There was a really interesting study published in the American Journal of Cardiology in 1999 (Lead author – Arangino et al) where they studied 17 healthy women and found that when you compare 1 mg dose of melatonin with placebo, melatonin seemed to reduce noradrenaline levels after 5 minutes of standing.
So based on these data, researchers started wondering whether Melatonin may work in POTS patients. In 2014, a group of scientists from Nashville, Tennessee published the results of a study of using Melatonin in POTS patients. This study was published in the Cardiovascular therapeutics journal and the lead author was Elizabeth Green.
The researchers took 78 patients with POTS and gave them placebo and 3 mg Melatonin on separate days. They then measured the heart rate and blood pressure changes from a sitting position to a standing position every hour for four hours after taking the medications. They also wanted to assess the patients’ symptom burden before and at 2 and 4 hours after being given the medications.
In terms of symptoms they were interested in 9 symptoms which often patients complain of. These include: mental clouding, blurring of vision, shortness of breath, chest discomfort, tremulousness, rapid heart beat, lightheadedness, nausea and headache.
The results were interesting in that the patients had a modest but significant reduction in standing heart rate compared to placebo. This reduction in heart rate was noticeable only 2 hours after administration and it was by about 7 beats/min. There was however no significant change in blood pressure. The other interesting result was that patients did not seem to report improved symptoms despite the reduction in heart rate.
So overall, it appears that melatonin may in conjunction with other heart rate lowering medications offer more effective control of standing heart rate. It would have been interesting to see what would have happened if they had used the melatonin at night rather than in the morning as this is the time when melatonin works most harmoniously with the body. We clearly need bigger studies to see whether melatonin given in the right way could help patients. – but the problem is that we won’t have such studies for several years and patients continue to suffer in the meanwhile. Many of my patients have asked me about Melatonin but unfortunately in the UK, melatonin prescription is very tightly regulated. In the US however it is easily available over the counter and some of my patients who have used it have found it to be helpful. I am going to set up a poll on my facebook account (@yorkcardiologist) to find out what patients’ experiences with melatonin and I will try and post the results of the poll in a week or so. If you have tried it please consider voting in the poll.
I hope you found this useful and once again thank you for all that you do for me.
Tags: POTS, postural orthostatic tachycardia syndrome, melatonin