diagnosis or treatment for my 15 year old with tachycardia.

What is her heart rate at rest?

IF she is not in an arrhythmia, but is in NSR, then the HR you cite is problematic in my opinion...and I am very much a non-expert. Her heart is trying to beat in normal sinus rhythm, but at a maximal rate for several hours at a time. This is like running a 5 km foot race at top speed, sprinting speed, and then feeling like a truck has run over her afterwards. No wonder!

I think you need to see a pediatrician, if this hasn't happened already, and have that person refer you for a second opinion. Just not from the same cardiologist.

My most urgent suggestion is that she have her thyroid hormone levels checked immediately. I would hope this has been done but have seen obvious causes of tachycardia like this overlooked. Hyper thyroidism is very common, especially in females and can be a cause of tachycardia and a fib both. It is treatable. Her heart rate is extremely high and I can’t imagine any cardiologist taking a cavalier approach to her problem. Her primary care doctor can order, the thyroid hormone levels and you would have results within a day or two. If that hasn’t already been done. .

My middle kid (female) had a heart rate of 140 at rest for awhile and then it went back to normal rate, mysteriously. I believe she had POTS from the tilt table test though the nurse turned around too quickly and didn't see the bp drop. Twenty years later she still has moments of near fainting in heat, because it dilates blood vessels and lowers blood pressure, I assume. She just recently went to a cardiologist for the first time in decades due to lupus.

My oldest kid (male) had fast heart rate after exercise and saw a pediatric cardiologist. I honestly forget why. They were very concerned and we called in his heart rate from the school nurses' office every day for awhile, after exercise. That too mysteriously righted itself.

I would find a really good pediatric cardiologist. Your daughter has had EKG, echo, stress test and svt and POTS are ruled out. What issue was found with the stress test?

I would ask what is causing the low blood pressure since that can make the heart rate go up, as I understand it. @gloaming knows more! I assume she is hydrated and you said she is taking salt.

I really hope you can find a doctor who listens. We found it could be hard to find doctors to take problems seriously with young females. The doctor should definitely test thyroid, cortisol, autoimmune markers, anything that could be contributing and whatever was found on the stress test must be relevant.

The BP can drop because the heart is beating so fast it cannot fill with blood. OR they may be wrong in assuming this is not POTS or SVT. It’s certainly in the range of SVT, especially if it starts suddenly. I’m curious what has been done in the ER for her. Something is seriously wrong, IMO, that this is allowed to continue by her cardiologist. I would consider taking her to the ER of your local university hospital or children’s hospital where someone takes this seriously. I would also have her avoid activities that bring on the tachycardia until this gets figured out. She could pass out, sustain a head injury, fracture, etc. This is dangerous! I hope you get the attention she deserves!!!

@slkanowitz and @kdwest422 I think I had the cart before the horse. Since the low bp follows the tachycardia, it would seem that the fast heart rate lowers bp as @slkanowitz described, not the other way around as I suggested!

Does she wear a smart watch? Has she done a patch monitor for a month? It seems you are documenting. Maybe it will help take this seriously if a cardiologist can see it. Again, what did the stress test show?

It's hard but the suggestion above to avoid anything that raises the heart rate seems prudent.

Please. Today. Find a different Cardiologist. It could very well be only a matter of time before a heart rate like that churns up a clot. As a School Nurse- I would have a hard time allowing a student with these symptoms to participate. Was she cleared during the time that she was having this many symptoms?
This sounds very scary. Maybe even ask for a Loop Recorder to be implanted to monitor continuously.
I'm sure you've been asked this a gzillion times- but seriously, does she consume very much caffeine? I am the biggest critic of Energy Drinks in all ages. But, I have the loudest voice to teach kids/adolescents about the dangers of them.
Many blessings and hopefully you can find the right Cardiologist to help get to the bottom of what is going on.

The cardiologist did full blood work and already ruled out hyper thyroidism. The only thing that was off on the blood work was her hemoglobin level was a little low so she has been taking iron since July. Thanks for the response

Thanks for all the information. Unfortunately, she is under one of the best pediatric cardiologist. Apparently, people drive 8 or 9 hours to see this doctor.

The stress test was the one with the pulmonary function and her lungs were cleared and they said they were no breathing issues. This is what we were told about the stress test:
- at level two kids her age have a max heart rate of 142. When she started level 2 she was already at 145 heart rate.
-then at the final stage of the test her heart was at 218 and her blood pressure was tanking.. she got to 82/49 and the test was stopped.
- we were told there clearly is an issue but the doctor was going to go back and review her blood work and the results from the halter moniter she wore for 10 days again
- The conclusion from that was that there was no clear signs of why this was happening and no wires to fix.
-no medication would be given at this time because of how low the blood pressure got
- we were to recondition the heart meaning getting her heart rate up to 130 for 2 1/2 hours a week and then as high as we can get it for 30 minutes. So we did this for about a month before she started band camp (which we were cleared to start by cardiologist)
- we were told to restrict her to 3 hours a day and that it was just conditioning it faster.
-nothing has improved and I can't even get an appt

I cannot take beta blockers or calcium channel blockers due to low blood pressure so I sympathize. But maybe ask the cardiologist- if you have access!- if low bp will still be an issue if the heart rate is slowed by meds.

Doctors seem really nervous about these meds with low bp. I have afib and got put in the ICU due to bp for an episode while most people just stay home!

Can she wear a patch monitor (much easier) for a month, and during band camp?

How are her hormones (I had PVC and SVT heart issues before my period until menopause)? Thyroid and cortisol levels? I hate to ask but any eating disorder? OOPS just read that blood work was done

ps The cardiologist's caution about meds may be warranted due to low bp. Her heart rate is not arrhythmic so maybe a clot is not likely.