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Resting Tach/Exercise Intolerance

I'm hoping someone can help. I'm a 42 yo female who has been athletic my whole life. About six months ago I noticed that I couldn't run or play ultimate frisbee with much gusto. The low exercise tolerance seemed to be getting worse and I finally went to the doctor. For the last 1.5 months, I have resting tachycardia (80-90 bpm) and very little exertion will send my heart rate to 160 (e.g. walking up a hill for 15 seconds). I have had an intense medical workup.

The following diagnoses have all been excluded:
anemia, thyroid, cardiac disease (normal angiogram, right heart cath, echo, bubble echo), endocrine (blood work up all normal), pulmonary function (so far nothing on cardio pulmonary exercise test, hi-res chest CT).

They are looking into mitochondrial myopathies (will schedule an EMG study and possibly do a muscle biopsy).

The exercise intolerance is getting to be a huge factor in my life. They put me on atenolol to see if that increased my aerobic capacity because I basically have no reserve. The beta blocker successfully lowered my resting rate but did not produce any increased exercise tolerance.

Does anyone out there have any similar experiences? I would really love some feedback. I'm an accomplished scientist and teacher. I know this isn't a stress response (I've been asked).

Thanks in advance!
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21064 tn?1309308733
Sounds like you have had a thorough cardio workup and with great results.  The fact that you're blood tests are normal is also excellent.  I'm at a loss as to what could be causing your decreased exercise tolerance.  The one things that comes to mind is peri-menopause.  I'm not suggesting anything in particular, but I'm wondering if a hormone imbalance could be at the root of what's going on.  Otherwise, I'm just not sure...Sorry, I can't be of more help.

I do know that beta blockers have a tendency to lower the HR, but also to cause fatigue.  Has your intolerance increased since beginning the BB?
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Avatar universal
Hi. I have MM and had the same problems with my heart rate that you do. Seems that I have gotten an autonomic neuropathy that is secondary to the MM. I also take beta blockers (Inderal LA, attenalol did not help me). Did they do a tilt table study to see if your blood pressure was falling with the increase in pulse? After surgery once, I spent two months virtually bedridden because I started passing out when I stood for too long (to get to the bathroom and back to bed was it). Anyway, my mom was an RN and she is the one who did "tilts" on me and found it and then the internal med doctor at the base, admitted me to the hospital and got me tested and on meds. (they first used florinef - miserable, made me gain weight and only let me stand up about 20 mins.)
Don't give up the testing and ask for referrals if you cannot get an answer where you are. Take care and God Bless. P
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