Syncope or seizure in 6 mo puppy

We've been having quite the time with our puppy. I'm not sure what is related, so I'm going to explain what's been happening in the last 5 weeks.

We were awakened Oct 16 at 5am to find her vomiting and covered in feces in her crate. She wouldn't stop vomiting so we took her to vet emerg. We had x-rays taken to rule out a blockage, and nothing abnormal was found. They gave her an injection to stop the vomiting, 7 days of flagyl and we fed her only bland food for a few days.

Three days later she passed out while playing outside - she was excited, then fell over and was out for 10 sec (no loss of bladder or bowels), but got up slowly and continued as if nothing happened. We went to our regular vet and she couldn't detect anything when listening to her heart, but mentioned several possibilities (incl. heart disorders, vagal syndrome) and suggested we wait-and-see if it happens again. Her stools still weren't normal (this was at day 6 of flagyl rx), so we did 10 more days worth of flagyl and sent stool for testing. Results showed giardia, so we did 7 days of panacur, which has resolved stool issues.

We had her scheduled to be spayed 2 weeks later (which was 2 weeks ago), but blood tests showed very high levels of creatinine - 2.74 - so she was sent home. The vet suspects too much protein in her food (Acana grain-free - 33%), so we've been feeding her low protein weight-control formula since. She went back on Wednesday this week and her creatinine was much lower, but still too high for surgery - 1.83.

Tonight while out for a walk, she fell over and was out for only a few seconds, but urinated. She got up, stumbled a bit and kind of lay back down for a few seconds, then was on her way, again as if nothing happened.

What could be the cause of her syncope (or could it be seizures)? The breeder had both parents tested and both are ARVC negative. She says a few of her puppies have had vagal syndrome. Should we be having an EKG or Holter test done at this point?

[Dr. Carol Osborne, DVM]

Your puppy needs to be seen by a veterinary heart specialist. The vet will run chest x-rays, an ultrasound of your dogs chest and an EKG to help determined the actual problem. A congenital heart and/or liver shunt or another problem such as vagal disorder may be the underlying issue.

Seizures may or may not be involved but my 1st step would be with a veterinary cardiologist.

Dr Carol Osborne, DVM