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Questions about IST

I have a mild form of IST.  I have been reading quite a bit about it in medical journals and I am confused by one thing in particular - the heart rate leading to a diagnosis of IST:

Some articles say that IST can only be diagnosed with a constant daytime resting heart rate of 100 or more AND a 24 hour heart rate average of 90 bpm or more.

However, I have found quite a few articles, written by cardiologists saying that IST is a resting heart rate of 100 or more AND/OR a heart rate of 100 or more on minimal exertion such as standing up or walking slowly.

Now, I am no expert, but if the second definition of IST is taken, then a lot of people have IST.

One of the questions posted to the forum cardiologists recently concerned standing heart rate.  He said that the average increase was 10 - 15 beats.

Take a person with a resting heart rate of 85 (which is in the normal range). If they stand their heart rate could well rise by 15 beats to 100.  According to the journals I have been reading, this equates to IST.

When walking, even slowly, it should increase HR again.  Surely this is not IST?  This does not make any sense to me.  
5 Responses
365304 tn?1210697927
Well I'm no expert either. But I will say this being a very active young man I started to get the symptoms of IST really flushed feeling low blood pressure perspirating dizzy blurred vision. Every symptom there is for it really I seem to have really really bad. It took 5 months for finally find someone that knew what it was and it was a cardiologist that diagnosed me with IST. My heart rate is never at a CONSTANT high mine can be normal      and then just decide to starting going up. Up to the point my BP drops and all that.What  seporates people with IST is that it doesnt take activity to spur the heart to beat faster. It can do it on its own. With that said things like adrenaline and other normal exercise Ex Walking and things of that sort have a quicker greater effect on our heart it kicks into overdrive really before it needs to. Pearsonally for me it does it for a while after exercise also... takes a while to slow things down again. You have to look at the more specifics of IST because MILD IST is like you say hard to distinguish between normal heart action and IST. I hope this helped somehow im still new to it I was only Diagnosed 3 weeks ago. In my case its pretty severe when its bad its really bad and the symptoms really pile on.
Avatar universal
Hi, I am a 23 yr old female, in great health very athletic. I work at a local hospital and am running around on my feet for 12hr shifts taking care of my patients. I was working one day and started 2 feel funny. We weren't very busy that day so I was basically just walking at a normal pace. I was having trouble breathing and I felt like my heart was going to jump out of my chest because it was going so fast and hard. I checked my heart rate at it was 130 just walking. I sat down for a few mins and then thought nothing of it. The next day I was working. Again walking at a steady pace. I got very light headed and thought I was going to pass out. I was shaking and breathing very fast and hard. Again I took my heart rate and it was 165. I told a nurse I was working with and she immediately made me sit down take deep breaths and she took my BP. after sitting down for about 45mins my heart rate was only down to 140 and wouldn't go down any lower. They immediately wheeled me down to the ER. Long story short even after my ER visit, and them flooding my veins with 2 bags of IV fluids, my resting heart rate was up in the 120s. I went to see a cariologist here at the hospital and did a stress test, and an Eco. After 9mins of walking on the treadmill my HR was 190. He then put me on beta blockers. This was all back in January of this yr and I am now on 75mg of extended release Toprol. I am extremely tired sometimes sleeping up to 20hrs a day. The toprol for the most part has been keeping it under control, but the longer I am on the meds the more my symptoms start to return. I have a feeling this is either getting worse or my body is just getting used to the meds. The meds also increase my fatigue. I used to workout about 3hrs a day and now I can barely get through a 20min workout and I have to take frequent breaks to catch my breath and let my heart rate slow down some before continuing the workout. So no I have been developing chest pains that radiate through to my back in between my shoulder blades and go up into the sides of my throat and up into my jaw. Also, my feet tend to get very red and puffy looking when I walk or stand for awhile. My cardio doc recently suggested to do a sinus node modification procedure and he referred me to the EP. After speaking the the EP he made it very clear that he was not going to do the procedure until my quality of life is so poor that I can basically not function anymore. I feel like this is progressively getting worse and I am developing more and more symptoms. I want to get this under control before it gets too bad. I am going to go get a second opinion and see if there is more we can do, but I feel like the beta blockers are really just a bandaid not a cure because even just doing little things like putting a load of clothes in the wash or sweeping the floor my heart rate shoots way up. Sometimes even just sitting on the couch reading it jumps way up. Any opinions or suggestions? Should I be concerned about this, because I am but the doctors don't seem to be? As a 23 yr old, my 60 yr old mother has more energy than me and that should be the opposite. Is sinus node modification the way to go? I am ready to get back to my life! Thanks!
Avatar universal
It sounds like you have POTS postural orthstatic tachycardia
1142137 tn?1301912430
hey im also 23 and was diagnosed wednesday..listening to you talk reminds me of me....you now for the longest time, i thought i had afib along with it..and still suspect, but no need to get into all that. anyways, i totally feel your pain. my dr put me on a 5-10 mg corgard. he says its basically to put a lid on the problem and avoid side effects. and i have to say, second day, this stuff is helping. im slightly tired but its doing the trick. my heart rate used to be average 96 bmp but now its about 76..kinda nice when my kids are screaming and my heart doesnt go bolistic. anyway let me know whats going on with you, as i see this post is sort of old..i wanna know someone who had an ablation for this...
Avatar universal
Hey there back in may of 2014 I had an ablation of the heart!! Let's just say it didn't work!! Just now on top of everything I'm swelling!! I am 32 so I understand your worries!! I have been dealing with this for three years and yes it only gets worse!! Sorry good luck!!
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