Heart Failure in Dogs and Cats: The Later Stages

Most families come to this article after a diagnosis of heart failure, or after a frightening night when their pet couldn’t catch their breath. Either way, you’re probably trying to understand what the coming weeks and months may bring.

In dogs, heart failure usually comes from one of two problems: a leaking heart valve, called mitral valve disease¹, or a weakened heart muscle, called dilated cardiomyopathy. In cats, it’s usually hypertrophic cardiomyopathy, a thickening of the heart muscle. That condition is more common than many people realize. In one study of healthy-seeming cats at rehoming centers, about 1 in 7 had it². Some cats with this kind of heart disease live a normal lifespan without problems from it, but for others the first sign is a crisis³.

This article covers what the later stages of heart failure usually look like, how to keep track of your pet’s respiratory rate at home, how to keep them comfortable, what an emergency looks like, and what families weigh as they think about the decision ahead. It’s part of our series on common end-of-life conditions.

We’ll start with what heart failure means, and how it changes as it moves into its later stages.

Heart failure means the heart can no longer keep up with what the body needs, and fluid starts to build up in or around the lungs. Veterinarians describe heart disease in four stages, using the same letters for dogs and cats^1,​3:

• Stage A – The pet is at risk, but there’s no heart disease yet.
• Stage B – Heart disease is there, often found as a murmur or on a scan, but there are no signs of heart failure yet.
• Stage C – The pet has, or has had, signs of heart failure.
• Stage D – The end stage, when the signs of heart failure no longer respond to standard treatment.

In dogs, mild valve disease can stay quiet for a long time⁴. This article is about stages C and D, when heart failure has begun and, eventually, when treatment can no longer keep it under control.

Once heart failure begins, the first signs in dogs usually involve breathing: breathing faster than normal, restlessness, trouble breathing or a cough¹. As it advances, many dogs grow weak, tire after a short walk, eat less and lose weight. In one study of dogs euthanized because of heart failure, most had shown weakness, coughing, a poor appetite, weight loss and labored breathing⁵. Losing muscle along the back and hips is common too. In another study, about half of dogs with heart failure had lost muscle this way, and it went along with less time⁶. Some dogs also develop a swollen belly from fluid, or start fainting, as the disease moves on^1,​4.

Cats often show it differently. The most common sign is labored breathing, but some cats only hide or stop eating³. Because cats are so good at hiding illness, their heart disease may not be noticed until it causes a crisis.

For dogs and cats alike, treatment usually means more medication over time, with changes along the way as the disease progresses. Knowing what the stages mean often leads to the question families ask next: how much time do they have?

Honest answers here come as ranges, not promises. In one study of dogs with end-stage heart failure from valve disease, half lived longer than about nine months, but the range ran from a few days to more than two years⁷.

In cats, the ranges are even wider. In an older study, half of the cats first seen in heart failure lived longer than about a year and a half, with some living only days and others many years⁸. A more recent study found that cats with fluid building up around their lungs, rather than in them, tended to have less time⁹.

These numbers come from specialty hospitals and particular groups of patients, and your pet may do better or worse. Our article on understanding survival times and life expectancy explains how to think about numbers like these. Whatever the numbers say, one of the most useful things you can do from day to day is watch your pet’s breathing.

Of everything families can do at home, counting breaths while their pet sleeps has the most research behind it. Veterinary heart guidelines call a rise in resting breathing rate the best early warning that heart failure is getting worse¹. In a study that followed dogs as they developed heart failure, their breathing rate, at home and at the clinic, rose more than anything else measured, and it rose just before the heart failure began¹⁰. In another, the counts families took at home were the most useful way to tell whether treatment was working¹¹. The good news is that it’s easy to learn: in the research, most families found counting simple^12,​13.

Things to consider:

• Wait until they’re sound asleep – Breathing is faster when a pet is awake, even resting¹², so count when they’re deeply asleep, not right after a walk or play.
• Count each breath – One rise and fall of the chest is one breath.
• Time it – Count for 30 seconds and double it, or count for a full minute.
• Write it down – Our free app, Hospet, can log each count so you can see the trend over time. A notebook works too.

To know whether a count is high, it helps to know what’s normal. In a study of healthy adult dogs, the average was about 13 breaths a minute while they slept, and no dog averaged more than 23¹². Dogs with heart disease that hadn’t reached heart failure weren’t much higher¹⁴, and healthy cats generally stayed under 30¹³. Even dogs and cats whose heart failure was well controlled on medication usually slept at around 20 breaths a minute¹⁵.

Most stable pets sleep under 30 breaths a minute, and veterinary guidelines for cats use 30 as the target to stay under³. Your veterinarian will give you your pet’s number, and what matters most is a change from your pet’s own normal. If the count climbs above that number, or keeps creeping up over a few days, call your veterinarian. If your pet is struggling to breathe, go straight to the emergency vet.

Coughing is one of the signs families notice most in dogs, but it can be misleading. Many dogs with valve disease also have airway problems, and an enlarged heart can press on the airways. In one study of dogs with valve disease, coughing went along with those airway changes and with an enlarged heart, but not with heart failure itself¹⁶. Veterinary guidelines make the same point: a heart murmur in a coughing dog doesn’t necessarily mean the cough comes from heart failure¹.

So a cough is always worth mentioning to your veterinarian, but a rising sleeping breath count is the better clue. In cats, the main thing to watch is the breathing itself³. Watching closely is one part of caring for a pet with heart failure, and keeping them comfortable is the other.

Much of the comfort care that helps any sick pet helps a pet with heart failure too, and our article on keeping your pet comfortable at home covers it in detail. Its breathing section, for example, suggests a cool, calm room, a fan they can lie in front of, and a harness instead of a collar. A few things matter especially with heart failure.

Things to consider:

• Help them keep eating – Losing muscle is common in heart failure, and veterinary guidelines note that it’s much easier to prevent than to treat. Simple things can help, like warming food, mixing wet food with dry, or offering a variety of foods¹. Our comfort care article has more ideas for a pet who’s eating less.
• Keep things calm – Heat and excitement make breathing harder. For cats, guidelines on heart disease recommend gentle handling, a quiet space and a box or bed to hide in³.
• Make medications easier – Giving several medications a day can be hard on everyone, and especially on cats. In a survey of families of cats with heart disease, worry about the stress of giving medications grew with the number of medications¹⁷. Ask your veterinarian whether the schedule can be simplified, and see our comfort care article for tips on giving medications.
• Tell every vet about their heart – In one study of cats with this kind of heart disease, heart failure sometimes followed fluids given through a vein, anesthesia, surgery or steroids⁸. Make sure any veterinarian who treats your cat knows about their heart.

Medications are the foundation of treatment for heart failure, and they often need adjusting as things change. Medical advice isn’t something you should get from the internet, so questions about them belong with your regular veterinarian or your pet’s cardiologist, who know your pet’s history. Even with good care, though, heart failure can bring sudden bad moments, and it helps to know what an emergency looks like before one happens.

Some changes can’t wait for a phone call in the morning. Go to the emergency vet right away if your pet is struggling to breathe while resting, if your cat is breathing with their mouth open, if their gums look pale, gray or blue, or if they collapse.

Because a crisis can come with little warning, it helps to plan for one now, while things are calm. Ask your regular veterinarian what to do if your pet’s breathing gets worse at night. Find out where your nearest 24-hour emergency hospital is and how long it takes to get there. And talk as a family about what you would want if it happens. As we put it in our webinar “When Is It Time? Understanding the Euthanasia Window”, “It’s better to get a plan in place so that if you are in a crisis situation where now you’re having to navigate this, you’re not making these intense, scary decisions under that duress.” Our article on preparing for the unexpected walks through what to plan.

Emergencies are one way heart failure shows it’s moving on. More often, the signs build gradually.

Heart failure reaches its end stage when the signs keep coming back even with treatment^1,​3. These are some of the changes that can mean things are moving in that direction.

Signs to watch for:

• A rising breath count – Sleeping breaths creeping up over days or weeks^1,​10.
• Signs that keep coming back – Coughing, labored breathing or a swollen belly returning again and again, despite treatment⁵.
• Eating less and losing weight – A poor appetite, or a thin back and hips, even if they’re still eating^5,​6.
• Weakness and tiring quickly – Needing to stop after a few steps, or no longer wanting to walk at all⁵.
• Fainting – Collapsing or fainting spells, which can be a sign of advancing disease⁴.
• Restlessness – Pacing, or trouble settling down to rest¹.
• Hiding or skipping meals, in cats – For some cats, withdrawing or not eating are the main signs³.

In a study of dogs with valve disease seen by their regular veterinarians, the signs families can see at home, like coughing, tiring easily, eating less, breathlessness and fainting, were the ones that predicted which dogs would die of their heart disease¹⁹. In other words, what you notice at home matters.

No single sign means it’s time, though. What matters is the overall picture and how it changes. Keeping track of good days and bad days alongside the breath counts, in Hospet or a notebook, makes those changes easier to see. Researchers have even built quality of life questionnaires specifically for dogs and cats with heart disease^20,​21. Our article on tracking your pet’s quality of life explains how to get started, and the section of our comfort care article on when comfort isn’t enough anymore describes more of the general signs.

If you’d like help putting a plan together, our veterinarians offer an in-home quality of life consultation. In a full, unrushed hour in your home, we can see how your pet is breathing and resting in their own space, and you’ll leave with signs to watch for and clear next steps. As those signs build, it’s natural to start wondering how the end will come.

Whether their pet will simply pass away in their sleep is one of the hardest questions families ask. Some pets with heart failure do. But we want to be honest with you, because it matters for the choices ahead: with heart failure, no one can promise a peaceful death, and death often comes suddenly.

In a study of nearly 30,000 dog deaths in UK veterinary practices, heart disease was the most common cause of death that came on its own, without euthanasia. About 1 in 5 dogs who died of heart disease died that way, compared with about 1 in 12 dogs overall²². In another study, of dogs with valve disease followed by their regular veterinarians, half of the dogs that died of the disease died suddenly, and the other half were euthanized as their signs got worse¹⁹.

Cats face the same uncertainty. In a large international study of cats with hypertrophic cardiomyopathy, more than half of the cats that had a heart crisis and then died, died or were euthanized on the day of that first crisis²³.

These studies don’t tell us what those sudden deaths were like. What we do know is that when heart failure runs its course, it’s usually breathing that becomes the problem, and struggling to breathe is distressing for a pet and frightening for the family watching.

Veterinary end-of-life guidelines take that seriously. They ask veterinarians not to let a pet die naturally without discussing euthanasia and making sure other ways of easing discomfort are in place²⁴. That’s why many families with a heart patient choose to plan their pet’s goodbye before a crisis, while their pet is still comfortable and the family can be together. Our article on letting a pet die naturally vs. hospice vs. euthanasia covers the options in more detail. Even so, choosing when is rarely simple, and heart failure brings a few things to weigh that other conditions don’t.

Heart failure is often unpredictable. A pet can seem almost like themselves between bad spells, which can make planning a goodbye feel too early. Our article on the euthanasia window describes how unpredictable conditions often push families toward the comfort side of the window, simply because they can’t guarantee they’ll be able to keep their pet comfortable. In one study of dogs euthanized because of heart failure, signs that kept coming back despite treatment were among the most important reasons for the decision⁵.

It’s natural to worry that a crisis will come while you’re at work or asleep. Where you live matters too. As we said in the webinar, “A family that lives near an emergency room that’s open 24 hours a day and is usually accepting patients, that’s a different calculus than somebody that lives further away.” A long drive is “a long time for your pet to be in a situation where they’re clearly uncomfortable,” and “if you want to avoid that emergency room and you live further away, you may have to make the decision a little sooner just to ensure that that’s the case.”

Our own family knows how hard this is. In the same webinar, Mike Hodge, a companion animal doula who owns Healing Touch with his wife, Dr. Kendra Hodge, shared the story of Pooh Bear, the dog they had for as long as they’d been together. Here it is in his words:

“He was a golden doodle, about 13 or so. And as he got older, he started to develop some cardiac complications. We tried to do our best to monitor. We tried to do our best to keep an eye on things, but what I can tell you is that we ended up uncomfortably close to ending up in an emergency room. And the same human factors that impact these decisions caught up with us as well. In our case, Dr. Kendra’s sister was moving back to the States after living overseas, so our plan was to wait until she was back so she could say goodbye.”

“Despite the fact that Dr. Kendra is an in-home euthanasia veterinarian, and despite the fact that I talk with owners about quality of life every day, the reality was that our desire to put this off a little longer caused us to nearly wait too long. If it can happen to us, and we do this every day, it can happen to anyone.”

If something like that has happened to you, Mike’s words from the same talk are worth holding on to: “please, please, please give yourself grace.”

Heart failure treatment tends to grow over time. In one study of dogs with end-stage heart failure, most needed their medications changed again and again, and by the end they were taking a median of five⁷. For cats, giving medications can be especially hard, and families’ worry about the stress of it grows with every medication added¹⁷.

That’s a fair thing to weigh. Some pets aren’t open to being medicated, and that makes treating a disease like heart failure difficult. It’s OK for that reality to influence where you fall within the euthanasia window, because you have to be able to manage the disease to keep your pet comfortable.

Whenever the time does come, it can help to know what the goodbye itself will involve. If you’re considering a goodbye at home, What Happens During In-Home Euthanasia walks through the visit step by step, and our guide to preparing for an in-home euthanasia covers the practical side.

Heart failure can move slowly for a while and then change quickly, which makes it one of the harder conditions to plan around. Counting your pet’s breaths, knowing what an emergency looks like, and talking with your veterinarian about a plan for a bad night can all help you feel more prepared.

Lean on your regular veterinarian or cardiologist for the medical side. And please be gentle with yourself. Living with the worry of a sudden crisis is hard, and it’s OK to ask for help with it.

→ Embracing the Emergency Room: Preparing for the Unexpected
Why ending up in an ER isn’t a failure, and how a small amount of planning can give you back the things that make a goodbye a good one.

→ Keeping Your Pet Comfortable at Home
Practical comfort care for a sick or aging pet, from footing and bedding to eating, breathing and medications.

→ The Euthanasia Window: Understanding When It’s Time
Why there’s no single “perfect moment,” and how to think about timing as a window rather than a moment.

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