Is this POTS or another type of Tachycardia?


Senior Member
East Sussex
POTs has always been a mild syndrome for me, not causing severe nausea and dizziness/fainting etc. More just OI and a bit of a funny head upon standing + 30BPM HR increase.

But a couple of weeks ago I took a high dose intensive course of PRObiotics and started to experience a couple of issues e.g. I became Dairy intolerant for 3 days (IBS-D) which I don't usually have. Then over the past week I've had increasing Tachycardia/POTS which has become quite intense.

My usual HR resting is: 60BPM, sitting: 70-80bpm, standing: 90-100bpm, walking: 115bpm
But it has gone up to: 80-90 Resting/Sitting, Standing: 105-110bpm and Walking 120bpm+

Additionally to HR, my heart is thudding and chest can become quite tight/strained which is uncomfortable and unsettling. I actually remember having something like this when I first became ill with ME after an infection - I had an ECG and it revealed Sinus Tachycardia which was put down to 'anxiety' yet later in my research i realised that a lot of infections can cause this.

I have read some advice to lay flat to relieve it but interestingly when I lie down it is as bad as 90BPM. According to this page: It makes it more likely to be IST - Inappropriate Sinus Tachycardia.

My diagnosis is ME/CFS from the NHS but I do have positive Armin labs results for Borrelia, Mycoplasma, CPn, Coxsackie. So I have a theory that the probiotics may have charged up my immune system and rattled these infections, or its just rattled my immune system, OR because I have leaky gut there is either some die off or translocation of bacteria into the blood stream.

High dose Vitamin C helps to lower HR by about 10BPM for a few hours, so I feel that this could be something viral/bacterial.

Any other ideas? Usually I am mostly housebound but able to go out a few hours a day for walks etc. but at the moment I am totally housebound because if I do any exercise it flares the POTS up really badly and I can't sleep.


Senior Member
many POTS patients have also high resting HR. Especially hyperadrenergic which is more linked to MCAS.

For IST you need to have daily average 100+ even during night (from what I remember)

but your POTS seems borderline, you should also check your standing BP to see if it drops, as it could be OHypo and not POTS.
or do a proper tilt table test.


Senior Member
South East, England
My cardiologist diagnosed me as POTS with features of IST. I assumed it was sneaky talk to justify prescribing Ivabradine, but I later discovered there is literature suggesting IST and POTS overlap, thought of by some as two points on a spectrum disorder.

Your description is very typical of an acute POTS flare for me. In my case usually a viral infection/reactivation, or just payback from doing too much the day before. My resting HR will increase in those scenarios.