could constant tachycardia be harmful?

[rcr5810]

I am a 26 year old female and for the past 48 hours I have had a heart rate of between 115-149. and blood pressure fluctuating from low to high. I have not felt dizzy but at time short of breath with not really chest pain per say but can definitely feel my heart beating hard. I had an allergic reaction about a week and a half ago and was given prednisone upon leaving the ER, told to take 2/day for 5 days which ended on sunday 11/20/16. I did have an ekg which showed sinus tach w/T-wave abnormality ( I work in a hosp ) I am not sure if to be concerned with a high heart rate all the time or if it has to do with coming off the steriods? could you please advise?