If you want to know the condition of the actual coronary arteries, then the only true way is an angiogram. In 2007 I had an emergency stent placed, and it was seen how my left artery was totally blocked, probably had been for years and I was 46. Now, a month after that, I had a nuclear scan. This looked fantastic and my cardiologist said if the nuclear scan was done first, then he wouldn't want to see me again. The reason? because I had formed collateral vessels to feed the deficit areas. So a nuclear scan can make things appear normal, but in reality the arteries could be a major mess. The best way to know for sure is to get inside the arteries and look.
Is he been treated by a Lipid Specialist ? It seems a too simple treatment for those levels.
Unless that his father suffered a Heart Attack, SD normally it is not caused by lipids.
If there is not inflamation, the risk for heart attack is reduced. Check value of sC-RP and tumoral factors.
Jesus
Was his stress test a nuclear stress test? If not, that may be a good place to start. It will show any areas where blood flow is diminished in his heart and will find CAD 97% when it is present.
Jon