Health Rising recently had a nice article published on Nov 1, 2013 on the research of Dr.Visser on this common symptoms of CFS patients. Later in the month there was also a video.
Reading the article, I noted that catecholamines appears to be a significant part of the symptom. Catecholamines is a family of chemicals consisting of epinephrine, norepinephrine, dopamine and hydrocortisone: cortisol. This caused me to wonder what we knew about the microflora and catecholamines. A search on PubMed found 1880 articles — too much information for most people!
Articles summarizes what I was expecting “These results indicate that gut microbiota play a critical role in the generation of free CA[catecholamines] in the gut lumen.”  and a treatment that some would like: ” Dark chocolate reduced the urinary excretion of the stress hormone cortisol and catecholamines and partially normalized stress-related differences in energy metabolism (glycine, citrate, trans-aconitate, proline, beta-alanine) and gut microbial activities (hippurate and p-cresol sulfate)…. a daily consumption of 40 g of dark chocolate during a period of 2 weeks is sufficient to modify…” 
And their impact on species typically overgrown in CFS is significant , which is why stress often worsen CFS symptoms — the overgrowth increases.
It is interesting to read the NIH list of items that increases catecholamines (and thus risk of palpitations)
- Acetaminophen (Tylenol, Paracetamol, Anacin)
- Calcium channel blockers
- Nicotinic acid (large doses)
- Tricyclic antidepressants
The only thing listed for reducing were prescription drugs. However, a little research on PubMed found
- Aswagandha – with caution about large dosages: “Increase in catecholamine content in the heart and aortic tissues and their decrease in adrenal glands are unfavourable effects of high doses of ashwagandha” 
- Rhodiola Rosea (Rosavin) has several appropriate articles:
- Magnolia bark
- “The crude extract of magnolia bark, an herbal drug, inhibited the secretion of catecholamines” 
During the research I found 1 2013 article: “Plant-based medicines for anxiety disorders, part 2: a review of clinical studies with supporting preclinical evidence“, which list some familiar herbs and some new-to-me ones that were deemed to be effective in the studies reviewed (Yes — an already researched list!). I am assuming that their mechanism is reducing catecholamines levels.
- Piper methysticum [Kava]
- Matricaria recutita, [German Chamomile]
- Ginkgo biloba, [Ginkgo]
- Scutellaria lateriflora, [Blue skullcap]
- Silybum marianum, [Milk thistle]
- Passiflora incarnata, [Purple Passionflower]
- Withania somniferum, [Ashwagandha]
- Galphimia glauca, [Thryallis]
- Centella asiatica, [Centella]
- Rhodiola rosea, [Rosavin]
- Echinacea spp., [Echinacea]
- Melissa officinalis [Lemon Balm]
- Echium amoenum [Borage]
Each has different chemicals, so it you have regular palpitations — you may wish to discuss with your medical profession about trying each of these for a week to see if any has a positive effect.