Do you get chest pain during exercise or sudden stress?
Without pain, you are probably looking at tight cholesterol control to lower the risk of the plaque getting any larger (or indeed any of the OTHER...we always have several...getting big enough to interfere with good circulation.)
With pain, a probably next step would be catheter angiography to locate and angioplasty the lesion.
A good regimen of cardiac aerobics (high heart rate) is a good idea to stimulate the formation collateral circulation in the area that is undersuppplied by the affected artery.
The good news are thhe words like "small" "limited" and "low likelihood" all indicate that no further intervention is needed in the near future....but it should certainly put you on high alert.
How are your blood lipid numbers? Did your cardio man recommend any drugs? Gosh, and you were trying to get off atenolol...angina is one of things it's good for, symptomatically anyway.