Hi, Judith! It's been a long time since we heard from you. I don't know what was going on with your husband, but think it unlikely that he was slipping into a coma. That usually happens at the very end, when a patient is extremely ill. Frankly, I would still tend to think it was cardiac related and that he should follow up with his cardiologist.
It's possible that his pacemaker may need to be tweaked, which is why I mentioned his seeing a cardiologist.