I have a 9 year old daughter. Healthy and atheletic. Last July she had a heart rate of 285. Er gave meds then an ice bath and it came down. Did blood work everything was normal said she had svt. We seen a heart dr kept track and decided on atenolol 25mg daily. She started on this in Dec. No side effects, no problems till now. She s so tired pale with dark circles under her eyes, gets sweaty, weak, falls a sleep in class, can t keep up at dance recess sports, irregular heart rate, it sometimes went low even before medication. Sats drop sometimes too, blurry vision. All tests normal echo was good, ekg perfect, cmp, bmp, cbc diff, thyroid, kidney,liver,iron,sugar, all normal. She s getting worse not better. I have a gut feeling is more then svt but Idk where or what do look for now