Have been on med for 1.5 years. the last 7 months heart rae has ...

I have been on this medication at 25mg for almost ten years. Just recently I have been experiencing a lot of dizzy spells followed by shortness of breath and a feeling of impending doom. These symptoms are more apparent in the day, and less in the evening. I take the Atenolol in the morning. Maybe I am experiencing a long term complication of the med, or maybe my body has changed, but nevertheless, my cardiologist has advised me to cease taking another dose after a holter monitor test.