So sorry to hear of these developments!
It sure sounds like a herx to me - especially since your issues occurred on two different abx.
That said, would you consider taking Hawthorne? It's a food-grade herb that's great for cardiac issues. The longer one takes it, the stronger the heart becomes.
www.drweil.com/drw/u/REM00040/Hawthorn-Dr-Weils-Herbal-Remedies.htmlwww.herbwisdom.com/herb-hawthorn-berry.html