Granddaughter's fluctuating heartbeat

[Barb77]

My eighteen year old granddaughter has a continually fluctuating heartbeat.  Even while resting, it can fluctuate from 80 to 120 and back to 90 within a minute (seldom going below 80).  She has had tests for thyroid and anemia - all of which came back normal.  She has also had an EKG, Echocardiogram (sp?), and several other tests, all of which came back normal.  Right now she has on a monitor (for 30 days); however, she has not had any feedback from this testing yet.  

This condition - which has been going on for over nine months - has made her tired and a little listless.  She is unable to do any physical exercise, because even the slightest activity raises her heart rate (sometimes as high as 150).    

Thank you in advance for any input.  

[Michael J. McWilliams, M.D.]

It depends on the results of her tests but it sounds like inappropriate sinus tachycardia.  If all her tests come back normal except the changes in her heart rate, that is the likely cause.  It is difficult to say what the cause is.  It is not really a heart problem but an imbalance in the autonomic nervous that regulates heart rate.  In some people the condition improves.  Beta blockers or calcium channel blockers ares sometimes used to control the heart rate, but the symptoms of fatigue often remain.  At this point you probably need to wait for the results of her cardiac work up.  I hope this helps.

[Barb77]

Thank you.  Your comments were very helpful.