Since the nuclear test is positive, this has to be confirmed with coronary arteriography for full evaluation and rx.
Especially, in your case with previous cabg, you want to make sure that the grafts are still open. If not, angioplasty
/stent or redo-cabg may be options to be considered after angiogram
. Medical rx for all you know, maybe be the better recourse, depending upon angiographic findings.