I am 70 years of age and have had a previous TIA and under blood pressure meds for 20 years. My normal rate has been 58. Lately, I have been having an accelerated heart beat of 110 to 120 periodically. It is accompanied by dizziness and shortness of breath. I also feel quite exhausted by midday. I am on Letrozole, Cardura, Atenolol, and bumex, as well as 20 mg of Zoloft. Could any of these be causing this to happen?