Like mammo suggests, this sounds like it could be a carotid artery problem. I'd start request from your primary physician a Carotid Ultrasound, It's possible that the same plaque that plugged his heart artery is doing the same with the arteries going to the brain. His symptoms you describe sound a lot like what are called TIA's, or tiny strokes.
A stress test isn't designed to show problems with the carotid arteries. Yes, a stress test in most cases would show a re-blockage of a stent, but not always as I've been told.
Best wishes. Let us know what you learn.
How would they check to see if the stent had collapsed and wouldn't the stress test show this?
Has his cardiologist checked to make sure the stent has not collapsed? Have they checked his Carotid arteries? It sounds to me like there is a lack of blood flow somewhere going to his brain (Carotid) or elsewhere. Maybe the arteries that were only 30% blocked, are now blocked more? I know how frustrating this is, and I would not stop until I got answers, definitely a second opinion! Stress tests never tell the whole story, so I wouldn't rely totally on that. Because your husband is so young, his doctor doesn't appear to be taking this seriously, but with his history, this needs to be taken very seriously! Find a new cardiologist who will listen to you both and do the necessary tests to find out what is going on. Remember, they work for us, expect them to do an excellent job. I think this one needs to be kicked to the curb!