Hi there, over the last 4 days I have developed a high heart rate and have a constant dull pressure on the left in my chest, did ECG was normal except the high heart rate it was 96 bpm resting heart rate,doctor started me on atenol 25mg a day to be taken once a day,I am unsure if this is anxiety related or heart related so gonna do further tests later as soon I reach my city on the weekend,in the meanwhile the 25mg once a day for the last 2 days doesn t seem to be making a huge difference,how long does atenol take to start seeing a diff to a 1st time user and Shud i up the dose a lil or wait for a bit