On atenolol for 4 days days now for hbp and pulse rate averaging between 55-70. before averaged in 80s. cause for concern?

>50bpm OK if no symp: Atenolol is a rate controller(B-Blocker) and a BP med. Part of the BP effect is slowing rate. A pulse rate >50 is adequate as long as with activity your heart rate increases significantly & there are no dizziness symptoms. If so You are in good range. I suspect if you walk up a hill your heart rate will increase to >80bpm. Great about B-Blockers is when you stop climbing, low HR&BP quickly return.