My ten year old Brittany male, adopted 18 months ago, has had a thunder phobia that he's gotten much better about over time. Twice in the past three months he's had panic attacks when the weather was perfectly fine and there was nothing new or unusual in our home or routine. The other night he had his second incident -- panting extremely hard, pacing, drooling, eyes wide. We took him out for a walk but he didn't calm down. I sat with him on the sofa and he peed, which he's never done except when he had a series of panic attacks for three days a few months ago. At that time, after the third attack, we took him to the vet and they did blood work, EKG and some basic neurological tests -- nothing unusual. By the time we got him to the vet he was fine, and he's been fine since until this weekend.
I gave him one of his thunderstorm pills and just held him and massaged his ears and he eventually settled down and went to sleep. The whole incident took about two hours. I'm worried about the strain on his heart and the fact that we can't imagine what's setting him off. His environment hasn't changed, our routines haven't changed, there have been no storms, no loud noises. I see no indication of depression in him -- his appetite is fine, he bounces up in the morning for his walk, he goes nuts when we come home at night, he gets four or five walks a day and he's very social with people and other dogs, he sleeps about the same as he always has, although is preference for where to sleep seems to change every few months. I can't imagine what's bringing this on, and I'm really worried that there might be something wrong with him neurologically.
Any ideas or suggestions about what this might be or what more to do? Thanks