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I was told by my cardiologist that I have IST, but after reading up on POTS I am uncertain. I started taking my blood pressure the other day with my husband's wrist blood pressure cuff. It also has a heart rate display on it. This is what I found:

After big meal 114/69 hr 131

feel normal 113/71 hr 74

standing up after getting out of bed 112/70 hr 149

So what do you think? Thanks in advance for any opinions.

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Of course I am not a Dr. so I can only share my experience.

Is your cardiologist an electrophysiologist? If not, I would recommend seeing an EP cardiology specialist.

Perhaps you can either discuss with your Dr. what you've found here on the internet or print some info off to share with him/her if you feel you have a good relationship with the Dr and they will be open to listening to you. (Some Dr's are great about this and others have bruised ego's and don't like patients bringing ideas to them because it makes them feel inferior somehow).

The first thing I would recommend is a cardiac tilt table test. This will provide valuable info as to what your heart rate and blood pressure do while lying down, standing up and under physical stress. The tilt table is not a conclusive diagnostic tool and there are both high numbers of false positives and false negatives. The key is #1 making sure the test is performed properly (you increase your odds on this factor by going to an EP) and #2 the Dr.'s knowledge of various autonomic disorders to ensure they know how to interpret the test results (many Dr's misinterpret because they don't know enough info about these disorders).

Though the test in and of itself is not a conclusive test it does give very valuable information.

I would take that test and then go from there once you know the results.

It can be very difficult to distinguish POTS and IST. Again, an area most Dr's do not address properly because they do not have the knowledge. IST can be a symptom of POTS or other underlying autonomic problem or it could be the result or symptom of something else.

The best advice I could give you in that regard is DO NOT allow anyone to do ablation surgery on you until you have further evaluation and testing. The majority of cases with those who have POTS or NCS the procedure is contraindicated and will often make people worse.

In my case the other thing that gave us a lot of info was wearing a 30 day cardiac event monitor. This allowed me to record several episodes over a months time and the way it works, the Dr gets a printout of your cardiac rythmn that shows what/how your "IST" develops, how long it lasts and how it "corrects" itself (if it does).

I would start with asking for these two tests and then go from there. You may at that point, depending on the results, want to try to consult with one of the 'experts' in the field.

Do you have any other symptoms aside from the IST?

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There is some overlap with these 2 conditions, at least in diagnostic terms. I would be careful before I would accept an IST dx if I had doubts.

I was diagnosed with IST before my POTS diagnosis. I was diagnosed by an electrophysiologist. The only test I had was a 2 week event monitor. It only picked up sinus tachycardia because I only activitated it when I was having tachycardia. Since my office EKG was normal, and I was very nervous in his office (my resting pulse was in the upper 90's) he diagnosed me with IST. That turned out to be a very bad thing. I knew nothing about arrythmias and never thought to tell him that my normal resting pulse was in the low 60's (which pretty much exlcudes a dx of IST). Many electrophysiologists won't dx you with IST if you have a resting pulse below 100.

Anyway, he started me on a beta blocker, which worked but caused me huge asthma problems. He then lowered the beta blocker and added a calcium channel blocker. I felt like I was going to die. My blood pressure, which was always low/normal plunged to 75/40.

A doctor friend of mine was insistent that I had been misdiagnosed. He sent me to an internist who did other basic tests, like a 24 hour Holter monitor (which showed that my pulse was always normal when I was resting, but would shoot up upon standing, with exertion, or if I stood in one place for too long). I also had a stress test and echocardiogram that showed my heart was structurally normal. I then went to an electrophysiologist my doc friend picked for me. He diagnosed me with POTS in less than 10 minutes. I didn't need a TTT because my blood pressure demonstrated enough just from going from sitting to standing in the office ( I only get pulse pressure narrowing when I go from sitting to standing).

I also had lots of other issues that I had never connected to my arrythmia, ie: IBS, urinary frequency, heat intolerance, acid reflux, vision problems,....it never occurred to me that all these things could be linked, but they were. Do you have any other symptoms?

I would ask you what tests you had that made your doctor arrive at the IST conclusion? Is he a cardio or electrophysiologist? IST is really a dx of exclusion, as is POTS to a certain extent since there are other conditions that can cause them. If you didn't have a thorough work up, I would pursue more testing. My electrophysiologist is a famous doctor (that's why my friend chose him), and while he is great at dx POTS, he isn't so great at treating it because it's an autonomic nervous system disorder that affects the heart, not a heart disorder. For the best possible treatment, going to see a doc that specializes in POTS (some are neuros some are electrophysiologists) would be a definitive way to get a correct dx.

Above all, do not agree to an ablation if you aren't sure you've been properly dx!!!!!! My first doc had me pretty much talked into one after the calcium channel blocker. I just happened to ask him (during a phone conversation) what would happen to my pulse since resting, it was so low. He was shocked that my resting pulse was in the 60's and said flat out, "I have made a mistake."

I was only diagnosed with POTS this August, so I am relatively new here. There are lots of others, like Poohbear, who are much more knowledgable. I just wanted to give you my 2 cents, since I was initially misdiagnosed. Good luck and follow your instincts.


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I went to my family dr. today for a sore throat and started talking to him about my tachy spells. I brought in the info that I had recorded above and some info I had gotten off the internet. I declare, I think I know more about it than he does. To his credit, he did suggest another wearing of the 24 hour monitor.

I have been to 4 or 5 cardiolgists. The last one was the one who said he thought it was IST. I started having symptoms in 1993 and since then I have have treadmill test, echocardiogram, 24 hour monitors, blood tests of all sorts (including thyroid).

When I wore the halter monitor for 24 hours a year or so ago my average hr was 92 and I had 3 ectopic beats (added beats).

I am beginning to believe I need to see an electrophysiologist but I don't know of any around here. I am closest to Cincinnati, OH. Anyone know of one near here?


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Very little to choose between IST and POTS as I understand it. Isn't POTS more dependent on posture, hence the POSTURAL ortho. tachy? Doesn't IST also cause more pronounced and sustained spells of tachycardia that are random rather than caused by movement?

THat's why my cardiologist in Scotland eventually concluded that IST was one possibility, but POTS was probably what I had.

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