Early Signs of CHF in Dogs: What to Watch For at Home

The earliest sign of congestive heart failure (CHF) in dogs is often a faster breathing rate while your dog is asleep, and it can show up before any cough or obvious tiredness. Other early signs include breathing that looks quicker or harder than usual at rest, restlessness at night, coughing, and tiring more easily on walks (Keene et al., 2019; Kittleson, 2024a).

Healthy dogs and dogs with heart disease that hasn't yet progressed to failure usually average fewer than 30 breaths per minute while sleeping (Ohad et al., 2013; Rishniw et al., 2012). A sleeping rate that stays above that level, or that climbs above your dog's own normal, is worth a call to your veterinarian the same day (Keene et al., 2019; Ljungvall, 2017).

Key points

• CHF isn't a single disease. It's what happens when a heart problem lets fluid back up into the lungs or body (Kittleson, 2024a).
• In dogs, the most common cause is degenerative mitral valve disease, which accounts for about three quarters of canine heart disease seen in North American general practice (Keene et al., 2019).
• Counting your dog's breaths during sleep is the most useful thing you can do at home. A rise above your dog's baseline has the best predictive value for heart failure that's starting (Keene et al., 2019).
• Coughing alone doesn't prove heart failure. Many dogs with heart murmurs also have airway disease, so a cough needs a veterinary workup (Keene et al., 2019).
• Fluid swelling the belly points to right-sided heart failure, and in dogs it is also the most common sign of fluid around the heart, which is sometimes caused by a tumor (Kittleson, 2024a, 2024b).
• Finding heart disease before failure starts matters. In one large trial, treating qualifying dogs before signs appeared extended the time until heart failure or cardiac death by roughly 15 months (Boswood et al., 2016).

Detailed explanation

What congestive heart failure actually means

A heart can be diseased for years without failing. Heart failure is the point where the heart can no longer keep blood moving well enough, and pressure starts backing up into the veins behind it (Kittleson, 2024a). "Congestive" refers to the fluid that collects as a result.

Which side of the heart is struggling decides where that fluid goes. When the left side fails, fluid seeps into the lungs. Dogs with left-sided failure most often cough, have trouble breathing, and can't exercise the way they used to, and some faint or collapse (Kittleson, 2024a). When the right side fails, fluid builds up in the abdomen, the chest cavity, the liver, and sometimes the legs (Kittleson, 2024a). Some dogs, particularly those with dilated cardiomyopathy, develop both.

Veterinary cardiologists stage the most common form of canine heart disease from A to D. Stage B dogs have a structural problem, often detectable as a murmur, but no signs at all. Stage C dogs have current or past heart failure signs (Keene et al., 2019). The "early signs" people search for are really the signs of moving from stage B to stage C, and that transition can be subtle.

Which dogs are most at risk

Mitral valve disease is the most common heart disease in dogs and is far more common in dogs under about 20 kilograms (44 pounds). It becomes more frequent with age; by 13 years, up to 85% of small-breed dogs have the valve changes, although having the changes is not the same as being in failure. Cavalier King Charles Spaniels tend to develop it younger (Keene et al., 2019).

Large breeds are more likely to develop dilated cardiomyopathy, in which the heart muscle weakens and stretches. It's inherited in Doberman Pinschers, with a reported prevalence of 58%, and cardiologists recommend yearly screening in the breed starting at three years old (Wess et al., 2017). Larger dogs with valve disease can be affected too, and they often progress faster than small dogs (Keene et al., 2019).

The early signs of CHF in dogs

Faster breathing during sleep. This is the sign most likely to appear first, and it's the one you can measure. Fast breathing is one of the classic signs of fluid in the lungs (Kittleson, 2024a). In a study of 63 dogs with mitral valve disease or dilated cardiomyopathy, respiratory rate was the second-best single predictor of CHF of all the variables tested, outperformed only by one specialized echocardiographic measurement (Schober et al., 2010).

Breathing that looks different at rest. You may notice your dog's sides moving faster, their belly pushing with each breath, or their nostrils working. The ACVIM consensus panel lists faster breathing, restlessness, labored breathing, and cough as the typical history in a dog with left-sided heart failure (Keene et al., 2019).

Restlessness, especially at night. Some dogs can't settle, change positions repeatedly, or prefer to sit or stand rather than lie on their side. Sleep changes are among the warning signs cardiologists teach owners to report (Ljungvall, 2017).

Tiring sooner on walks. A dog who used to finish the loop and now stops halfway, lags behind, or lies down early may have reduced exercise tolerance, one of the most common signs of left-sided failure (Kittleson, 2024a).

Coughing. A cough, especially one that's new or getting worse, can come from fluid in the lungs. It can also come from an enlarged heart pressing on the airway or from airway disease that has nothing to do with the heart. Because chronic airway disease is so common in the small, older dogs who also get valve disease, a murmur in a coughing dog doesn't by itself mean the cough is from heart failure (Keene et al., 2019). Read more about why dogs with cancer cough, since lung tumors can cause the same sign.

Eating less, a swollen belly, fainting. Loss of appetite, a distended abdomen, fatigue, and fainting are all on the list of heart failure warning signs (Ljungvall, 2017). None of these signs is specific to the heart, which is exactly why they need a veterinary exam rather than a guess.

How to count your dog's sleeping breathing rate

Wait until your dog is deeply asleep in a cool, quiet room, not twitching or dreaming. Count each time the chest rises for 30 seconds and double it, or count for a full 60 seconds. One rise and fall is one breath.

Do this several times over a week or two while your dog is well, so you know their baseline. Cardiologists suggest about ten counts to establish a normal (Ljungvall, 2017). In a study of 114 apparently healthy adult dogs, no dog's average sleeping rate was above 23 breaths per minute, and the authors concluded that healthy dogs rarely exceed 30 (Rishniw et al., 2012). In 190 dogs with heart disease that hadn't yet failed, average sleeping rates were also generally below 25 and seldom higher, and individual dogs' rates stayed stable from count to count (Ohad et al., 2013).

That stability is what makes this so useful. A single high count can happen during dreaming, in a warm room, or after a stressful day (Ljungvall, 2017). Repeated counts above 30, or a clear upward trend from your dog's own baseline, are the pattern to report (Keene et al., 2019; Ljungvall, 2017). Free phone apps exist for logging these counts, and our Dog Cancer Tracker can hold the numbers alongside other daily observations.

Your veterinarian may give your dog a different personal target. Dogs already being treated for heart failure often settle at similar rates; in one study, dogs with medically controlled CHF had a median sleeping rate of 20 breaths per minute (Porciello et al., 2016).

Why catching heart disease early matters

Sleeping breathing rate catches failure as it begins. Finding the heart disease before that, while your dog seems perfectly well, can change the timeline.

In the EPIC trial, dogs with mitral valve disease and an enlarged heart but no signs of failure were given either a heart medication or a placebo. The treated dogs went a median of 1,228 days before developing heart failure or dying of cardiac causes, compared with 766 days for the placebo group, a difference of about 15 months (Boswood et al., 2016). Current guidelines recommend treatment for dogs that meet those criteria, which are confirmed with an echocardiogram or chest X-rays (Keene et al., 2019). Treatment decisions belong to your veterinarian or a cardiologist; the point for owners is that a murmur found at a routine visit is a reason to ask about staging, not to wait for signs.

When the heart problem is connected to cancer

Two connections matter for families in our community.

Fluid around the heart, called pericardial effusion, squeezes the heart and mainly produces signs of right-sided failure, and cardiac tumors are one of its two most common causes in dogs. Hemangiosarcoma and heart base tumors are the most common cardiac cancers in dogs (Kittleson, 2024b). A swollen belly is by far the most common sign, and collapse can happen too (Kittleson, 2024b). If your dog has a swollen belly, pale gums, or sudden weakness, it needs prompt evaluation regardless of whether you suspected the heart.

Some chemotherapy can affect the heart. In a study of 494 dogs treated with doxorubicin, 4% developed clinical heart problems, but the rate was 15.4% in Boxers and other breeds prone to dilated cardiomyopathy. Fainting or collapse was the most common sign, and a few dogs developed CHF (Hallman et al., 2019). If your dog has had doxorubicin, mention it at every visit, and treat new breathing changes or collapse as urgent. Our overview of chemotherapy for dogs explains how oncologists plan around these risks.

Cancer also causes many of the same signs as heart failure, including fast breathing and panting, coughing, and fatigue. That overlap is why chest X-rays, an echocardiogram, or a blood test called NT-proBNP are used to tell the two apart. A normal or near-normal NT-proBNP in a dog with cough or breathing trouble strongly suggests heart failure isn't the cause (Keene et al., 2019).

When to contact a veterinarian

Go to an emergency hospital now if your dog:

• Is working hard to breathe, breathing with an open mouth at rest, or can't get comfortable lying down
• Has blue, gray, or very pale gums
• Faints or collapses, even if they recover quickly
• Has a rapidly swelling belly along with weakness

Call your veterinarian the same day if:

• Sleeping breathing counts are repeatedly above 30 per minute, or clearly higher than your dog's baseline
• A cough is new, getting worse, or worse at night
• Your dog seems restless at night, tires much sooner on walks, or stops eating

Book a regular appointment if your veterinarian has mentioned a murmur and you haven't discussed staging, or if your dog is a breed at high risk and hasn't been screened.

Questions to ask your veterinarian

• Does my dog have a heart murmur, and if so, what stage of heart disease does that suggest?
• Would an echocardiogram or chest X-rays help, and should we get baseline images now while my dog is well?
• What sleeping breathing rate should prompt me to call you?
• Could this cough be coming from the heart, the airways, or something else?
• Would an NT-proBNP blood test help sort out what's causing these signs?
• My dog has cancer. Could the heart be involved, and should we check for fluid around the heart?
• My dog has received, or may receive, doxorubicin. Should my dog have heart screening first?
• Should we see a veterinary cardiologist?

Sources

Boswood, A., Häggström, J., Gordon, S. G., Wess, G., Stepien, R. L., Oyama, M. A., Keene, B. W., Bonagura, J., MacDonald, K. A., Patteson, M., Smith, S., Fox, P. R., Sanderson, K., Woolley, R., Szatmári, V., Menaut, P., Church, W. M., O'Sullivan, M. L., Jaudon, J.-P., . . . Watson, P. (2016). 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, 30(6), 1765-1779. 

Hallman, B. E., Hauck, M. L., Williams, L. E., Hess, P. R., & Suter, S. E. (2019). Incidence and risk factors associated with development of clinical cardiotoxicity in dogs receiving doxorubicin. Journal of Veterinary Internal Medicine, 33(2), 783-791. 

Keene, B. W., Atkins, C. E., Bonagura, J. D., Fox, P. R., Häggström, J., Fuentes, V. L., Oyama, M. A., Rush, J. E., Stepien, R., & Uechi, M. (2019). ACVIM consensus guidelines for the diagnosis and treatment of myxomatous mitral valve disease in dogs. Journal of Veterinary Internal Medicine, 33(3), 1127-1140. 

Kittleson, M. D. (2024a). Heart failure in dogs. Merck Veterinary Manual, Dog Owners Version. Retrieved November 5, 2026, from https://www.merckvetmanual.com/dog-owners/heart-and-blood-vessel-disorders-of-dogs/heart-failure-in-dogs

Kittleson, M. D. (2024b). Pericardial disease in dogs and cats. Merck Veterinary Manual. Retrieved November 5, 2026, from https://www.merckvetmanual.com/circulatory-system/various-heart-diseases-in-dogs-and-cats/pericardial-disease-in-dogs-and-cats

Ljungvall, I. (2017). Home monitoring of dogs and cats in congestive heart failure [Conference proceedings]. World Small Animal Veterinary Association Congress. VIN. https://vin.com/doc/?id=8506403

Ohad, D. G., Rishniw, M., Ljungvall, I., Porciello, F., & Häggström, J. (2013). Sleeping and resting respiratory rates in dogs with subclinical heart disease. Journal of the American Veterinary Medical Association, 243(6), 839-843.

Porciello, F., Rishniw, M., Ljungvall, I., Ferasin, L., Häggström, J., & Ohad, D. G. (2016). Sleeping and resting respiratory rates in dogs and cats with medically-controlled left-sided congestive heart failure. The Veterinary Journal, 207, 164-168. 

Rishniw, M., Ljungvall, I., Porciello, F., Häggström, J., & Ohad, D. G. (2012). Sleeping respiratory rates in apparently healthy adult dogs. Research in Veterinary Science, 93(2), 965-969. 

Schober, K. E., Hart, T. M., Stern, J. A., Li, X., Samii, V. F., Zekas, L. J., Scansen, B. A., & Bonagura, J. D. (2010). Detection of congestive heart failure in dogs by Doppler echocardiography. Journal of Veterinary Internal Medicine, 24(6), 1358-1368. 

Wess, G., Domenech, O., Dukes-McEwan, J., Häggström, J., & Gordon, S. (2017). European Society of Veterinary Cardiology screening guidelines for dilated cardiomyopathy in Doberman Pinschers. Journal of Veterinary Cardiology, 19(5), 405-415.