Atrial fibrilation post triple bypass surgery risks and concerns after one incident?

A fib. Risk of emboli going to brain causing stroke. Rapid ventricular response(heart rate to high) may cause angina, dizziness, passing out, heart attacks, other heart irregular rhythms. Let you cardiologist manage case. Is complex to explain here. It is certainly manageable.
About 20% get it. Atrial fibrillation after cardiac and pulmonary operations is a known event. Medical treatment is often effective. May take several weeks to resolve, sometimes may require cardioversion.