By Dial A Vet Veterinary Team
Congestive heart failure (CHF) is what happens when a struggling heart causes fluid to back up into the lungs, chest, or belly. In dogs it most often shows up as fast, effortful breathing, and it can become an emergency within hours. The word "congestive" refers to that congestion with fluid. Understanding where the fluid goes, and why, helps owners spot trouble early. For the conditions that lead to CHF, see common types of heart disease in dogs. For staging and long-term home monitoring, see heart failure in dogs.
Key takeaways
- CHF means fluid is building up because the heart cannot move blood forward efficiently.
- Left-sided CHF causes fluid in the lungs (pulmonary oedema). Right-sided CHF tends to cause fluid in the belly or chest.
- Fast breathing at rest is often the first sign, before coughing or tiredness.
- Struggling to breathe, blue or grey gums, or pink frothy fluid from the mouth or nose is an emergency.
- CHF is usually manageable for a period with veterinary treatment, which is adjusted over time.
Why fluid builds up
A healthy heart pumps blood forward as quickly as it arrives. When a valve leaks badly or the muscle weakens, pressure rises in the chambers and the vessels that feed them. Raised pressure pushes fluid out of the blood vessels into surrounding tissue.
Left-sided failure is the most common type in dogs, usually caused by mitral valve disease or dilated cardiomyopathy. Pressure rises in the veins from the lungs, and fluid seeps into the lung tissue. Oxygen has trouble getting into the blood, so the dog breathes faster and harder.
Right-sided failure is less common. It can follow tricuspid valve disease, heartworm, lung disease that strains the heart, or fluid around the heart. Fluid tends to collect in the abdomen (ascites), giving a pot-bellied look, or in the space around the lungs.
Signs of congestive heart failure
- Sleeping or resting breathing rate that is higher than your dog's normal
- Breathing with more belly effort, flared nostrils, or an open mouth
- A soft or moist cough, often at night
- Restlessness, pacing, or reluctance to lie on one side
- Tiring quickly, lagging on walks
- A swollen belly or weight gain despite eating less (with right-sided fluid)
- Fainting episodes
Older small-breed dogs with a known murmur are the group most often affected, but large breeds with DCM can deteriorate quickly and sometimes show few warning signs.
When it is an emergency
Go to an emergency veterinary hospital now if your dog:
- Is working hard to breathe, especially at rest or lying down
- Has blue, purple, or grey gums or tongue
- Has pink, frothy fluid at the nose or mouth
- Collapses, faints, or cannot get up
- Has a rapidly swelling belly with breathing difficulty
Phone ahead if you can so the team can have oxygen ready. Keep your dog calm and cool, and avoid lifting them by the chest.
How vets diagnose CHF
A vet will listen for a murmur, abnormal lung sounds, and rhythm changes, and look at gum colour and breathing effort. Chest X-rays are the main way to confirm fluid in the lungs and to see heart size. A focused ultrasound in the clinic can quickly check for fluid in the chest, belly, or around the heart. Once the dog is stable, an echocardiogram, ECG, blood pressure, and blood tests help identify the underlying cause and guide long-term treatment. A very unstable dog may be given oxygen and treatment before all tests are done, because handling can make breathing worse.
How CHF is treated, in overview
Emergency care focuses on oxygen, rest, and medication to move fluid out of the lungs. Fluid in the chest or belly may be drained with a needle. After the crisis, most dogs go home on a combination of medications chosen by the vet to control fluid, support heart function, and reduce strain on the heart. Dogs on these drugs need follow-up checks, including kidney values and electrolytes, and the plan often changes as the disease progresses. Do not adjust or stop any heart medication without your vet's guidance, even if your dog seems much better.
Long-term management
- Count and record the sleeping breathing rate a few times a week, or daily after a change in medication.
- Know your vet's "call us" number for breathing rate and keep emergency hospital details handy.
- Keep regular recheck appointments and blood tests.
- Offer gentle exercise and avoid heat, which increases breathing effort.
- Avoid salty snacks and talk with your vet about appetite and diet.
- Use year-round heartworm prevention where recommended.
FAQ
Is congestive heart failure the same as heart failure?
Heart failure is the broad term. Congestive heart failure describes the version where fluid builds up, which is the most common way heart failure shows itself in dogs.
Can fluid on the lungs come back after treatment?
Yes. That is why home breathing rate checks and regular rechecks are so useful. Catching a rise early often allows your vet to adjust treatment before a crisis.
Why does my dog cough more at night?
Lying down can shift fluid and pressure in the chest, and an enlarged heart can press on the airways. A night cough in a dog with a murmur is worth reporting to your vet.
Talk with a vet
If you are worried about your dog's breathing or want help making sense of a CHF diagnosis, our vets can talk it through by video and help you decide how urgently to be seen. Book a consult at dialavet.com. If your dog is struggling to breathe right now, go directly to an emergency vet hospital.
References
- Keene BW, et al. ACVIM consensus guidelines for the diagnosis and treatment of myxomatous mitral valve disease in dogs. Journal of Veterinary Internal Medicine, 2019.
- Merck Veterinary Manual. Heart Failure in Dogs and Cats.
- American Heartworm Society. Canine Heartworm Guidelines.
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If your pet is having trouble breathing or has collapsed, contact a veterinary hospital immediately.