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!