Well, I would have to agree with the Doctors. Many times, patients don't even know they have a hole in the heart until they suffer a TIA or stroke and more tests are performed. Around 1 in 5 are caused by this and it isn't age associated. The important thing is that they have hopefully put him onto medication to help prevent further events. However, having said that, it could also be the blockage in the neck forming clotting material. Did they say how large the blockage is? what percentage of restriction?
With regards to the hole in the heart, which is a likely cause, there are basically three options. There is medication to reduce his clotting factor, there is open heart surgery to close it, or a newer technique using angioplasty to place a patch. This involves using a catheter like when they insert a stent.