Newly diagnosed IST: I was recently... - Arrhythmia Alliance

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Newly diagnosed IST


I was recently diagnosed with IST and really struggling with these sxs. Im having episodes of increased heart rate even with just sitting of 150-180 at times. When episodes occur initially cold clammy hands and feet, hot flash, very shaky, weak and short of breath. I get uncontrollable tremors, stomach cramping. Being treated with Atenolol. At times feeling weak, intolerance to minimal activity even when heart rate is down with medications. I was initially diagnosed in August and struggled for about 3 weeks then sxs improved and was doing much better for month of September up until several days ago and has flared back up. I was wondering if anyone else with IST would want to share there sxs with me. Still having some testing to make sure there is no underlying cause.

13 Replies

Sorry to hear about your diagnosis and that your struggling.

I also have IST and was diagnosed in April this year. I initially spent two weeks in hospital as I couldn’t even brush my teeth without my HR being 150 and the hospital recorded my HR being 150 in my sleep at one point!

They picked up a partial right bundle branch block when I was first admitted and also found I have a likely bicuspid aortic valve which is functioning normally and both are of no concern at all.

I’ve been reassured by my cardiologist that this IST isn’t life threatening and more of a pain to deal with! I am currently coping quite well and have cut out caffein completely as that didn’t help.

I really struggled for the first 3 months I’m now on 2.5 bisoprolol and 5 ivabradine and I can really control the condition with these meds other than now suffering from my HR dropping to the 40s. I also have exercise intolerance which sucks!!! I still go to the gym but I’ve just adapted.

However I do have the occasional episode where I almost faint, my lips or nails will go blue, sometimes my tongue goes limp, I go freezing cold and extremely pale and then my heart starts racing, my hands will go cold and clammy but after episodes I get flushed. These episodes have significantly reduced since being on meds. Im going to ask my cardiologist about possibly having a loop recorder implanted ( small device that sits under the skin and is basically a mini ecg that can stay in for 3 years) as I want to be sure sure that nothing else happens during my episodes.

I’ve been told that il eventually grow out of IST, I’m 18 so hopefully that’s the case. I just make sure I stay as positive as I can and I have continued with all my activities with what I used to do prior to diagnosis but I listen to my body and stop if I’m struggling to much.

cocapoo in reply to Hidden

Thank you so much for sharing. Do you ever have sxs when your heart rate is down in normal range? Sometimes I feel very shaky, weak , stomach cramping and loose stools when my heart rate is normal range with medication. I’m thinking I may not be tolerating the atenolol, but not sure. Because once I’m about 10 hrs outside of the taking the Atenolol those sxs improve but then heart rate increases again

Hidden in reply to cocapoo

No worries😊 Since being on my meds my resting HR is now in 40s-50s and I only really get my symptoms now if I do something like run up the stairs or go to the gym, things like that or when I have one of my episodes.

Sometimes in the mornings I wake up a bit shaky but that soon goes. Ivabradine is a great drug it’s fairly new but works a treat for people Who have sinus Arrhythmias as it only works if the heart is in sinus rhythm. I’m also on a beta blocker and this combo really helps! It takes a while to get the dosage and type of medication right but once you have found the right balance I’m sure you will feel much better.

I’ve been told to try and exercise which I have been and I honesty think that it helps! I really really struggled to start with I almost cried in the gym but I’ve adapted and my body is getting back Into the swing of things.i find cycling is the easiest form of cardio as well as swimming and I do go on the weights as well. I also surf and have been told to be careful surfing and being in the sea which is understandable! I have an Apple Watch so I can keep an eye of my HR and if it’s too high il stop for a bit. However I’m only 18 and was super active prior to diagnosis so I would recommend talking to a professional about exercise before hand! Hope this helps 😊

cocapoo in reply to Hidden

Thank you. I also have a sinus arrhythmia, all EKGs have shown sinus but of course fast rate. There has been ST depression when the rate is fast then resolves once rate slows down. I’ve had a full cardiac work up with no blockage shown. When you say exercise intolerance, do you have sxs with fatigue but heart rate is controlled and hard to exercise because of sxs? My heart rate has recently been more controlled with medications but still having sxs of fatiguing easily with things such as walking up stairs, lifting wet clothes into drier, especially activities with my upper body. My heart rate is in a normal range when doing these activities but still having sxs. I was physically strong prior to this and even had been jogging. I’m unsure why I’m having sxs with these activities and heart rate controlled. Is this something like you experience?


Sorry to hear you are struggling with IST. I have it as well and you can find a few of us here who do and it might benefit you to read some of our past posts.

Funny, what has worked for each person has been slightly different, but our symptoms are all fairly similar. There are a few whose heart rates are always high but mine is more like you describe. Mine would shoot up randomly and also for any sympathetic stimulation (eating, emotions, etc) and then sometimes get stuck at the higher rates, often for up to 6 hours or more. Exercise was tough because my rates were about 30bpm higher than should be and a few times a week it would get stuck for an hour or two afterwards. After 2 years of trying different meds, nothing had really helped all that much except maybe Ivabradine but it was causing other Arrhythmias in my case.

I was so desperate that I almost went in for an ablation knowing that the chances of it helping were very low. But on a random whim I took a half of a 25mg Metoprolol and it worked pretty well so now I take 12.5 at waking and around noon. None at night since my rates already dip into 40s.

It doesn’t solve all of my palpitations but it does make most days livable.

No one truly understands how miserable this condition really is. I describe it as having the feeling that you are on the starting line of the most important race of your life and you are experiencing all the physical symptoms that entails, except the gun never shoots so your just stuck there waiting. And then repeat that feeling about 30 times a day on a bad day or on an even worse day you may feel as though you did cardio for 8 hours straight.

Anyway, best of luck to you and I hope yours resolves itself and/or you find consistent relief from your symptoms. Keep us posted on here.

cocapoo in reply to 2k2d

Thank you for sharing. I’m know going to be started on Cardizem and stop the atenolol due to having sideffects. I don’t think my cardiologist has had many patients with IST so I appreciate as much input on the different medications.

cocapoo in reply to cocapoo

now(sorry for the typo)

2k2d in reply to cocapoo

Good luck with the cardizem! I think ist is pretty rare so if you continue to have troubles, get referred to a specialist, preferably an electrophysiologist who has dealt with ist.

Fred77 in reply to 2k2d

I dont think

IST that rare, my cardilogist had 25 pts with this

Now im her 26st pt, she said.

The problem is some med specialists , believe its anxiety,

Dont diagnosis just let people live with this exhausting condition.

2k2d in reply to Fred77

Good point. It's probably not that rare, just under diagnosed. It's just referred to as a "rare" type of SVT on the internet. And, unless you come across as an extremely stable person, the doctor going to assume it's just anxiety. I think the difference in anxiety vs IST is that anxiety can consistently raise the heart rate, but not by the large amounts seen in IST. Apparently heart rate shooting up 50-150bpm for laughing, eating, getting excited/nervous, light exercise, etc is not normal. I'm sure many people suffer from it and have no idea that's not normal. I'm pretty sure I had mild IST, or had it from time to time, before it ever landed me in the hospital.

Fred77 in reply to 2k2d

I don't think I've experienced rises in my pluses that much from laughing, but stress yes.

My last cardiologist didn't even pick it up, changed to a new one she picked it.up.straight away.

But.i do have a loop recorder in,

Thats was my choice before,


They can stay in up to 3 yrs.

I thought I was getting to old for this, IST early 40s .

Literature states

.it acures in younger people more.

Any thoughts

Also I have mild heart disease ,

Heard IST can get worse with this.?

2k2d in reply to Fred77

I have no idea about the heart disease part. I thought heart disease can cause similar symptoms to IST? But I wasn't aware IST could make heart disease worse.

Anyway, my IST wasn't majorly apparent until I was 38. I'm 41 now and it hasn't changed at all. When my meds wear off, it's back, so I know I'm not one of the lucky ones where it just mysteriously disappears.

I guess at least you have a loop recorder so if anything too weird goes on they will catch it.

Are you taking meds for your IST? Heart disease? Do they help at all? Ablation isn't supposed to be very successful yet for IST unless you want to modify the sinus node and have a very good chance of getting a pacer.

Fred77 in reply to 2k2d

Hi yes iam on a list of meds corlan 5mg twice daily,

For the IST

Micardis plus. Clorvesent , 12.5mg spiratone .

Angina spray when necessary.

The loop good, but it's a day surgery produce,

In Australia , can be done in some some public hospitals .

I got my done in a private hospital cost not that much,

Only the $500 access yearly ,

The rest was covered,

Had to play for the doctor that put me under it was like $700

To broke for private health now, had give it away.

Sorry I meant , I read if your heart disease gets worse. IST becames more frequent,

Or what you said,

It can cause similar symptoms to IST .

Cause of my loop she would be on top of iam sure.

I get monitored regularly via the loop thats reassuring 3 to 6 months checks.

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