Question on stent vs. medication tx

My father has just undergone a angiogram and was advised that his Right Coronary artery is 100% blocked. 8 years ago he had his first angiogram d/t tightening in the throat symptoms upon exersion. His angiogram at that time showed a very small occlusion in the lower aspect of the heart- resulting in the stable angina.
The lastest angiogram also revealed "new arteries" had formed and have compensated for the blockage somewhat. My question is : with 100% blockage and reduced blood flow as stated in the report from the angiogram should a stent not be looked at? My father's  ECG and Inhanced stress test were both negative. The blockage was only seen from the angiogram. What is the likelyhood in resolving this blockage with a stent therefore reducing or eliminating the angina symptoms?
My concern is, by not looking after this blockage and potentially waiting for another to develop elsewhere vs. just continuing to take medication to keep the angina "at bay"?