Atrial Fibrillation (AFib) Support Group
Atrial fibrillation (AF or afib) is an abnormal heart rhythm (cardiac arrhythmia) which involves the two small, upper heart chambers (the atria). Heart beats in a normal heart begin after electricity generated in the atria by the sinoatrial node spread through the heart and cause contraction of the heart muscle and pumping of blood.

The antibiotics however are a different story.
When I was given a zpac with Prednosone....I went into afib off and on for a month. Sautee, this sounds like what you are experiencing. Longer episodes and more frequent. Yours will probably be better soon!