Inappropriate Sinus Tach

[kdavidson1965]

What exactly is IST?  My thyroid med was decreased from 112mcg to 56mcg due to my heart racing.  I gained the hypothyroidism s/sx.  I went back to 75 mcg and starting to feel better.  A month ago, someone I knew, younger than me, died in front of me due to an aortic anyeurism (sp). This set into play a series of my heart racing, dizziness, and fear of fainting.  I was admitted to the ER with a HR of 123 and HTN 157/109-al sx resolved after 1mg of Ativan.  Never had blood pressure or heart problems in my life!  Cardiac workup showed Sinus Tach of 108 on EKG, nml echo, negatice urine results for adrenal tumor or pheochromocytoma, and no abnormal signs on 24 hr Holter with a HR of 80-92.  The doc said I have a "robust" beating heart and put me on Toprol 25 mg qd, 1/2 tablet.  My TSH has risen from 2.9 in October, to 3.0 in early January to recently 4.01.  Primary care doc says I am within normal limits for TSH, no need to increase meds, cardiologist says go to endo, which I am, and that I may need to increase thyroid meds to 100mcg.  
So, can hypothyroidism contribute to IST?  What is the best treatment for IST as the beta-blocker makes me feel like a slug all day-just not my energetic self anymore?  What are the long term implications of IST?  Can it be cured and what can I do to resolve this?  This has been very dibilitating being a nurse in medical sales and not able to drive with dizziness, racing heart and lethargy.  Thank you!

[cindy707]

Great post questionnone!  You about covered that one.....

[questionnone]

Hi, I was diagnosed with IST and basically IST is when your resting heart rate is high and it goes even higher with little exertion. It is really common for tachycardias to be associated with thyroid issues and that is one of the first things cardiologists/doctors/EPs try to rule out first. So if you do have an overactive thyroid it may be coming from that. After much research, doctors have told me that IST is not well understood and the cause of it is not well understood either. Some doctors believe it has to do with the sinus node of the heart and others think otherwise (deals with the nervous system to some). Some say that it improves with time in some patients (that is if your heart rate is only slightly higher than "normal") and some say medical treatment/ablation is the way to go. I would also like to tell you that sinus node modification ablation has mixed feelings by different EPs. Some EPs are strongly for it because they have seen good outcomes but some EPs believe beta blockers are the best bet for now because IST may have a chance of reoccurring post ablation compared to SVT ablations . What I learned from cindy707 and my own awareness is to talk to multiple doctors if you can. As far as your holter showing 80-90 bpm that is actually very good compared to mine. I am only at 80bpm resting when I am on a beta blocker. I am currently trying to find other causes of my IST (I have a neck injury that may be messing with nerves, black mold exposure, and other little things that I want to rule out.) I also heard of a doctor diagnosing someone with IST that they suspect to come from a viral infection which may be a cause for anyone (cold & flu?.)

[cindy707]

Hi read your post.....something just isn't right here.  If you are getting dizzy, cont. to have a racing heart and are tired and listless after you've been put on the meds those meds have to be changed or adjusted in decreasing the mg. by your heart doc.  Your heart rate was just a little above normal limits so i wouldn't stress it there as a nurse as you say you are you know the within normal limit range is 70-120 and if you came in at 123 not to worry especially if they caught that rate in an E.R., docs office etc. because we all know B/P goes up as does heart rate from anxiety while in those settings.  Your B/P however was definately on the high side and it sounds like the Toprol should do it but i want to remind you that Toprol is notorious for throwing out the exact side effects that you are having.  You may simply need to be given a smaller gun beta blocker like antenolol that has fewer side effects on the human body.....up to your doc.  Long term effects of IST is sort of like a crap shoot....you really don't know what you will be rolling here...obviously any probs. w. the heart and leave some residual effects but if you are on the right meds and pro active with seeing the heart doc you are def. decreasing the potential for probs.  People have IST for 30 years and are still doing great...many of who post on this forum.  You heart rate cardio work up looked amazing to me and your doc could be very very right in sending you the the endo doc....as we all know anything having anything to do with the thyroid can effect absolutely everything in your heart not to mention your body and mind. As far as your disease vs. the tach...if that is under control so will the tach be....keep your appt. and i would call your doc and tell them that the meds may not be working for you if you are having "breakthroughs" in regards to your racing heart and are lethargic and dizzy...no no no..............good luck

[elrav]

I as recently diagnosed with ST and my doc put me on diuretics.  They, combined with my blood pressure meds are supposed to level out my heart rate.  Hope this helps