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Dog Heart Disease Signs: What to Watch For at Home

Fudini ·

Owner watching a resting dog at home

The signs of heart disease in dogs include a cough, tiring faster on walks, faster or harder breathing, fainting, weight loss, a swollen belly and changes in appetite or sleep. The catch is that most dogs show none of them until the disease is advanced. So the most useful thing you can do at home is learn what normal looks like for your dog, then notice when it shifts. This guide covers the signs, the one home measurement vets ask for, which symptoms are emergencies, and how to hand your vet something better than “he just seems off.”

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Notice Changes in Your Dog’s Routine
Fudini’s collar tracks eating, sleeping, walking, and playing patterns, helping you spot changes to discuss with your veterinarian.

TL;DR

  • Most dogs with heart disease show no clinical signs until the disease is advanced, so small changes in routine matter.
  • Common signs: coughing, difficulty breathing, reduced stamina, fainting, weight loss, a swollen abdomen, and changes in sleep or appetite.
  • Count your dog’s breaths while asleep. A rate that stays above 30 breaths per minute is a reason to call your vet.
  • Labored breathing, collapse, or a bloated, painful belly (especially in a deep-chested breed like a Great Dane) means going to an emergency clinic now.
  • Write down what you see and when. Dated notes make a vet visit far more productive.

Table of Contents

Why heart disease is so easy to miss

A healthy dog’s heart has a lot of reserve. Early on, a leaking valve or a weakening heart muscle can be compensated for, and the dog carries on as usual. Veterinary sources describe exactly this: most dogs have no symptoms until the disease is advanced. In dilated cardiomyopathy (DCM), a veterinary cardiology update from WSAVA notes there can be a long preclinical phase, and that catching the disease early matters for quality of life and survival.

That is why a vet may hear a murmur at a routine exam before you have noticed anything. It is also why, when owners do spot something, it is usually vague: a dog who skips the last stretch of the walk, sleeps in a different spot, or seems a little flatter. Those are the changes worth writing down.

The signs of heart disease in dogs

The Tufts Cummings School of Veterinary Medicine lists the symptoms of heart disease as abdominal swelling, behavior changes, coughing, difficulty breathing or sleeping, fainting, rear limb weakness, reduced ability to exercise, altered appetite, and weight loss or poor growth. In plain terms, here is what that looks like at home.

Tiring sooner than usual

Exercise intolerance is one of the most common early complaints. Your dog still wants to go, but stops, lags behind, lies down on the sidewalk, or needs longer to recover after play. Because this creeps up over weeks, many owners blame age or a hot day. Compare against your dog’s own history, not against other dogs.

Dog pausing on a neighborhood walking path

Coughing

A cough is the sign people search for most, and it deserves a careful read. See the cough section below, because the cause is often not the heart.

Changes in breathing

Fast breathing while resting, belly muscles working with each breath, or restless sleep where your dog keeps changing position can all signal trouble. Dogs with fluid in or around the lungs often cannot get comfortable lying flat.

Fainting or weakness

A dog who collapses briefly during excitement or exercise, or whose back legs seem weak, needs a veterinary exam. Do not wait to see if it repeats.

Appetite and weight changes

Heart disease can cause a dog to eat less and lose weight, including muscle. A swollen belly is different: it can mean fluid buildup. If you are seeing a dog who eats less, our guide to dog eating less, red flags and what to do walks through the causes and when to call. If the scale is moving the other way, see how to track body condition and behavior before feeding more.

Sleep and behavior shifts

Sleeping more, sleeping less, pacing at night, or withdrawing from play can all be early, nonspecific signs. They also overlap with pain, arthritis and cognitive changes, which is why a vet needs to sort them out. For the cognitive side, see our piece on canine cognitive dysfunction signs.

Count your dog’s sleeping breathing rate

If you do one thing after reading this, do this. VCA Animal Hospitals explains that a resting or sleeping respiratory rate consistently above 30 breaths per minute is considered abnormal and may be an early indicator of congestive heart failure. The Merck Veterinary Manual adds a reason for counting during sleep: panting commonly masks fast breathing, so a awake dog’s rate can be misleading.

How to do it:

  1. Wait until your dog is deeply asleep or resting quietly, in a cool room.
  2. Watch the chest rise and fall. One rise and one fall is one breath.
  3. Count for 30 seconds and double it, or count for a full minute.
  4. Write down the number, the date and the time.
  5. Repeat on several days, so you know your dog’s usual range.

VCA says a consistently increased rate warrants prompt veterinary contact, and if it comes with other clinical signs, it may be an emergency. A single high count right after a dream or a hot afternoon is not the point. A pattern is.

Dog cough and heart disease: what the cough usually means

Owners searching “dog cough after exercise” or “dog coughing heart disease” often fear the worst. Here is the more nuanced picture.

The Merck Veterinary Manual states that coughing can occur with pulmonary edema, but in dogs it is much more commonly due to lung disease such as chronic bronchitis. Royal Canin’s veterinary academy notes that coughing originates from the airways even in cardiac patients, and lists tracheal collapse and infectious tracheobronchitis among the other possibilities.

That does not make a cough harmless. Tufts notes that in a dog already known to have heart disease, a cough can mean heart failure is worsening, with fluid in the lungs, particularly when paired with fast or difficult breathing.

A practical way to think about it:

What you notice What it could point to What to do
Cough after exercise or excitement, dog otherwise normal Airway or lung problems, or sometimes heart disease Book a vet visit; film the cough
Cough plus faster sleeping breathing Possible fluid in the lungs Count sleeping breaths and call your vet promptly
Cough in a dog with a known heart condition Possible worsening heart failure Contact your vet the same day
Cough with struggling to breathe, blue or gray gums, collapse Emergency Go to an emergency clinic now

A short phone video of the cough, plus your breathing-rate log, gives your vet far more to work with than a description.

Signs that need urgent care

Some situations should not wait for an appointment next week. Go to an emergency veterinary hospital, calling ahead if you can, when you see:

  • Labored or open-mouth breathing at rest, or a sleeping breathing rate that is high alongside other signs. VCA says this combination may be an emergency.
  • Collapse or fainting.
  • A cough that suddenly worsens, especially with fast breathing, in a dog with known heart disease.
  • A distended, hard or painful belly with retching (see the bloat section below).

If you are unsure, call your vet or the nearest emergency clinic and describe what you see. They would rather triage a false alarm than meet a dog in crisis.

Common heart conditions and what “stages” mean

Two conditions come up most. The Merck Veterinary Manual names myxomatous mitral valve disease (MMVD) and dilated cardiomyopathy (DCM) among the common heart conditions in dogs. MMVD is a degenerating valve that leaks; DCM is a heart muscle that stretches and pumps poorly.

Congestive heart failure (CHF) is not a disease in itself but a result: blood dams up in or around organs, making them function abnormally or become swollen with fluid. The same Merck page explains that heart disease is classified into stages A, B1, B2, C and D under the ACVIM consensus system. In rough terms, the early letters describe dogs at risk or with disease but no failure, and the later letters describe dogs that have shown, or are being treated for, heart failure. Only your vet, often with a cardiology workup, can place your dog on that scale.

Why this matters to you: staging explains why a vet may recommend monitoring a murmur with no medication, and why the plan changes once signs appear. Your home observations are one of the inputs.

Can dogs have heart attacks?

Not in the way people do. Human heart attacks usually come from blocked coronary arteries, which is uncommon in dogs. But sudden events happen. The Merck Veterinary Manual notes that dogs with heart failure can die suddenly from arrhythmias or acute events such as a ruptured chordae tendineae, the small cords that anchor the valve. So collapse in a dog with a murmur or known heart disease is always an emergency, whatever you call it.

Great Dane bloat: not heart disease, but just as urgent

Many people who search for heart signs in big dogs are also asking about bloat, so it belongs here. Gastric dilatation-volvulus (GDV) is a stomach problem, not a heart problem, but it can kill quickly and its early signs can look like distress from something else.

Cornell’s Riney Canine Health Center says owners of Great Danes should watch for non-productive retching, excessive drooling, pacing, and a distended, painful abdomen. The stomach twists, restricting blood flow and causing shock, and without medical and surgical treatment the condition is fatal. It is a life-threatening emergency in large, deep-chested breeds.

If you see these signs, do not wait to see whether they pass. Call an emergency clinic and go.

Prevention is a conversation for your vet when your Dane is young. Cornell’s soft tissue surgery service notes that a prophylactic gastropexy can be done in young dogs, attaching the stomach to the body wall so it cannot twist.

What we think about heart signs and daily routines

We build Fudini around one belief: the earliest clue is rarely a dramatic symptom. It is a quiet drift in how your dog eats, sleeps, walks and plays. Owners notice drift imperfectly. You see your dog every day, which makes gradual change nearly invisible. A vet sees your dog for twenty minutes, in a stressful room, which makes normal behavior invisible too.

What we think about heart signs and daily routines overview diagram

That gap is where a baseline helps. Whether you keep a notebook or use a sensor, the principle is the same: know the usual, then flag the unusual. We are careful about what that does and does not mean. A change in routine is not a diagnosis, and no collar can tell you your dog has heart disease. What a baseline can do is turn “I think he has slowed down” into “over three weeks his walks got shorter and he is sleeping more,” which is a sentence a vet can act on.

We also think alerts should be rare. A device that pings you all day teaches you to ignore it. Our approach is to learn each dog’s routine over weeks and speak up only when behavior moves meaningfully away from it.

— Denys

Where Fudini fits

Fudini is a wearable sensor collar with an iOS app. It tracks four behaviors, eating, sleeping, walking and playing, learns your dog’s normal routine, and alerts you only when it detects a significant drift. It does not rely on GPS. Its purpose is to give you a clear, dated record of changes to bring to your vet.

Fudini

You can see how it works on the Fudini App page, or read how we built it in our build log on teaching a neural net what a dog eating looks like. The app also has fact-checked pet care guides, which are free and carry no sponsored product pushes. Browse them in our dog health articles.

What to track and tell your vet

When you book a visit for possible heart signs, bring facts rather than impressions. VCA notes that recording sleeping or resting breathing rates can give an early clue of developing heart failure and help the vet manage the disease. Build a one-page summary:

  • Sleeping breathing rate: several readings across different days, with dates.
  • Cough: when it happens (after exercise, at night, after drinking), what it sounds like, and a short video.
  • Stamina: how far or how long your dog walks now compared with a few months ago.
  • Sleep: changes in where, how long and how restlessly your dog sleeps.
  • Appetite and weight: meals refused, treats ignored, any visible weight or muscle loss, or a swelling belly.
  • Episodes: any fainting, wobbliness or collapse, with the date and what your dog was doing.
  • Medications and supplements: everything your dog takes.

If your dog is a breed prone to heart disease, or your vet has already found a murmur, ask how often to recheck and what thresholds should prompt a call. Your vet knows your dog’s history; use that to set your own personal alarm lines.

FAQ

What are the first signs of heart disease in dogs?

Often there are none. When signs do appear, the earliest are usually reduced stamina, a new cough, faster breathing at rest and changes in sleep or appetite. Because these also fit many other conditions, ask a vet to examine your dog rather than guessing.

Can a dog cough from heart disease?

Yes, but it is less common than a cough from airway or lung problems like chronic bronchitis. In a dog already diagnosed with heart disease, a new or worsening cough, especially with fast breathing, can signal fluid in the lungs. Either way, a persistent cough merits a vet exam.

What is a normal sleeping breathing rate for a dog?

VCA considers a resting or sleeping rate consistently above 30 breaths per minute abnormal. Count while your dog is asleep and calm, and log it over several days. If the number stays high, contact your vet promptly.

Can dogs have heart attacks?

True heart attacks like those in people are uncommon, but dogs with heart disease can die suddenly from rhythm problems or a ruptured valve cord. Collapse in any dog is an emergency. Go to an emergency clinic immediately.

What are the signs of bloat in a Great Dane?

Watch for unproductive retching, heavy drooling, pacing and a swollen, painful belly. Bloat with twisting, called GDV, is fatal without emergency treatment, so go to an emergency vet right away. Ask your vet about preventive gastropexy when your dog is young.

Sources

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