TL;DR
The key signs of congestive heart failure (CHF) in dogs are faster breathing at rest or asleep, coughing, tiring easily, restlessness at night, fainting and a swollen belly. The single most useful thing an owner can do is count the sleeping breathing rate: dogs with heart disease that is not in failure, and dogs whose heart failure is well controlled, usually breathe under 30 times a minute asleep, so a rate that rises above 30 is an early warning. Most heart failure in dogs comes from mitral valve disease in small breeds or dilated cardiomyopathy (DCM) in large breeds such as Dobermanns. Treatment works: in the EPIC trial of 360 dogs with enlarged hearts from valve disease, pimobendan delayed heart failure by about 15 months and helped dogs live longer.
Signs of heart failure in dogs
| Sign | What you might notice |
|---|---|
| Fast breathing at rest | Over 30 breaths a minute while asleep or relaxed |
| Labored breathing | Belly working hard, flared nostrils, open-mouth breathing at rest |
| Cough | Often at night or after lying down |
| Tiring easily | Stopping on walks, lagging behind |
| Restless nights | Pacing, unable to settle, sitting up to breathe |
| Fainting | Collapse during excitement or exercise |
| Swollen belly | Fluid build-up, more common with right-sided failure |
| Weight and muscle loss | Especially over the back and hips |
| Pale or bluish gums | Poor circulation or low oxygen |
In a study of 369 dogs with DCM, the most common signs were breathlessness (67%) and coughing (64%), and 89% had an abnormal heart rhythm. Signs had usually been present for only about three weeks before referral.
Count the sleeping breathing rate
This is free, takes one minute, and is what cardiologists ask owners to do.
- Wait until your dog is sound asleep, not dreaming.
- Count each rise of the chest (in plus out counts as one breath) for 30 seconds and multiply by 2.
- Do it a few times a week and write it down.
In a study of 51 dogs whose heart failure was well controlled on treatment, the median sleeping rate was 20 breaths a minute, and only one dog was at 30 or more. Dogs with heart disease that has not yet caused failure also stay under 30. So a sleeping rate that climbs above 30 and stays there is a reason to call your vet that day, often before any other sign.
Causes of heart failure in dogs
Mitral valve disease (small breeds)
The mitral valve thickens and leaks with age. It is the most common heart disease in dogs and starts as a heart murmur your vet can hear. In UK practices, about 3.5% of dogs had a murmur consistent with the disease, and dogs under 20 kg had about twice the odds of larger dogs. Cavalier King Charles Spaniels are the classic breed: a heart murmur was recorded in 30.9% of Cavaliers in UK practice records. See Cavalier King Charles Spaniel lifespan.
A small-animal vet Morty has known for years, who asked us not to use their name, sees it constantly in small Poodles: "Toy Poodles are especially prone to mitral valve disease." See Poodle lifespan.
Dilated cardiomyopathy (large breeds)
In DCM, the heart muscle weakens and the heart enlarges. In the 369-dog study, Dobermanns and Boxers were most commonly affected, 73% were male, and median survival after diagnosis was 19 weeks. Screening before signs appear is the best defense. See Doberman lifespan.
Stages of heart disease
Vets use the ACVIM stages for valve disease:
| Stage | Meaning |
|---|---|
| A | At risk (for example a Cavalier), no murmur yet |
| B1 | Murmur, heart not enlarged |
| B2 | Murmur, heart enlarged; treatment now helps |
| C | Heart failure now or in the past |
| D | Heart failure that no longer responds to standard treatment |
Treatment
Before failure: pimobendan
The EPIC trial randomized 360 dogs with valve disease and an enlarged heart (stage B2) to pimobendan or placebo:
- Median time to heart failure or cardiac death was 1,228 days with pimobendan against 766 days with placebo, about 15 months longer.
- Dogs on pimobendan lived longer (median 1,059 versus 902 days).
- Side effects were no different from placebo.
A 2025 analysis of 928 UK dogs with loud (grade IV/VI) murmurs found the same in everyday practice: over 5 years, 34.1% of dogs given pimobendan developed heart failure against 56.3% of those not given it.
This is why an X-ray or heart scan when a murmur first gets louder is worth doing.
In heart failure
- Diuretics such as furosemide to remove fluid from the lungs.
- Pimobendan to help the heart pump.
- Other heart medicines as the vet advises.
- Regular checks of kidney values and blood salts, because diuretics affect the kidneys. See kidney disease in dogs.
- Home breathing-rate counts to guide doses.
Living with a dog with heart disease
- Count the sleeping breathing rate several times a week.
- Keep your dog lean. Extra weight makes the heart work harder. See senior dog food for weight loss.
- Gentle, regular exercise, stopping before your dog gets breathless.
- Avoid salty treats and table scraps.
- Keep the muscle on. Dogs with heart failure often lose muscle; keep feeding well and ask your vet about diet. See muscle atrophy in dogs.
- Never stop heart medicines suddenly.
FAQ
What are the first signs of heart failure in dogs?
Usually faster breathing at rest or asleep, coughing, tiring easily on walks and restlessness at night.
What is a normal sleeping breathing rate for a dog?
Under 30 breaths a minute. Dogs with heart disease that is controlled typically breathe around 20 a minute when asleep; a sustained rise above 30 is a warning sign.
How long can a dog live with congestive heart failure?
It varies with the cause and treatment. With good medication many dogs with valve disease live comfortably for months to years, while DCM generally has a shorter outlook.
Can heart failure in dogs be prevented?
Not always, but treating valve disease at the right stage delays it: in the EPIC trial, pimobendan delayed heart failure by about 15 months.
Which dog breeds get heart failure?
Small breeds such as Cavalier King Charles Spaniels, Poodles and Chihuahuas often get mitral valve disease; large breeds such as Dobermanns and Boxers get DCM.
References
- Porciello F, et al. Sleeping and resting respiratory rates in dogs and cats with medically-controlled left-sided congestive heart failure. The Veterinary Journal. 2016. PMID: 26639825
- Boswood A, et al. Effect of pimobendan in dogs with preclinical myxomatous mitral valve disease and cardiomegaly: the EPIC study, a randomized clinical trial. Journal of Veterinary Internal Medicine. 2016. PMID: 27678080
- Pegram C, et al. Emulating the EPIC trial using VetCompass primary-care data: causal effects of pimobendan in UK dogs with grade IV/VI heart murmurs. PLOS ONE. 2025. PMID: 40531835
- Mattin MJ, et al. Prevalence of and risk factors for degenerative mitral valve disease in dogs attending primary-care veterinary practices in England. Journal of Veterinary Internal Medicine. 2015. PMID: 25857638
- Martin MW, Stafford Johnson MJ, Celona B. Canine dilated cardiomyopathy: a retrospective study of signalment, presentation and clinical findings in 369 cases. Journal of Small Animal Practice. 2009. PMID: 19037887
- Summers JF, et al. Prevalence of disorders recorded in Cavalier King Charles Spaniels attending primary-care veterinary practices in England. Canine Genetics and Epidemiology. 2015. PMID: 26401332
For individual health questions, your veterinarian remains the best partner.
