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Can a dog suddenly develop heart failure with no prior signs?

Updated on September 23rd, 2025

I belive my dog was poisoned and the vet is calling it heart failure. I think they are wrong. Will a dog have heart failure all at once with zero symptoms over the course of 2 days

2 Answers

Most Helpful Answer

Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on July 16th, 2017

I'm sorry your dog isn't doing well! Please keep in mind that I can't say anything for certain without seeing your dog in person, so my opinion comes from my experience. Dogs unfortunately can be very stoic about illness, and oftentimes they are very ill before showing any signs at all. It certainly is possible that your dog has been in heart failure for a while, and it's taken time for signs of it to show. As I said before, dogs can be very ill before showing symptoms and that does frequently happen in dogs with heart failure. Their heart will be failing, and it's only picked up when they suddenly develop exercise intolerance, coughing, or fainting when exercising. If you do feel the vet is wrong, then I'd recommend taking him into another vet for a second opinion. I hope this helps you!

1Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Dr Stafford, BVetMed, MRCVS
Veterinarian
There are different types of heart failure, sometimes it comes on gradually with signs but at other times they will be fine until suddenly they cant compensate and shoe signs of being in failure. Other times a chordae tendinae can rupture in the heart and you will see sudden onset of severe heart failure.
You neec to remeber that your vet is a qualifief professional who deals with many cases everyday. They do know a lot more about medicine than you. Yiu could ask your vet to explain exactly why they suspect heart failure over poisoning, maybe you will understand better if you see their reasoning.
But if you are still not satisfied you should take your dog for a second opinion as there is no point having it treated by someone you dont trust. That is unfair on both you and the vet.
1Pet Parents found this answer helpful

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