Long term effects

My daughter is 15 and was just diagnosed Ectopic Atrial Tachycardia.  The odd thing is that she is not experiencing any symptoms and we only discovered it through a routine physical.  Because she has no symptoms, they are saying she will likely not need medication or other methods to normalize the heart rate.  

My question is what is the long term effect of having a heart rate much higher than normal that spikes and drops so significantly?