Heart failure in dogs first manifests as a cough at rest or during sleep, unusual shortness of breath, increasing fatigue, and sometimes a swollen belly — but these signs generally appear only several months or even years after the actual onset of the disease. It is precisely this silent delay that makes early detection so crucial: the earlier the problem is identified, before the first visible symptoms, the more effective the treatment options and the longer the dog’s life expectancy. Here’s how to recognize the signs, understand the stages of the disease, and monitor your dog at home to not miss the right moment.
What is heart failure in dogs? #
Congestive heart failure (CHF) is not a disease in itself, but the consequence of an underlying heart disease that progresses: the heart can no longer pump enough blood to meet the body’s needs, causing fluid to accumulate in the lungs (pulmonary edema) or abdomen (ascites), depending on the side of the heart affected. It is this excess fluid that causes the cough, shortness of breath, and fatigue characteristic of the disease.
The two main causes: MVD and dilated cardiomyopathy #
Two heart diseases account for the vast majority of heart failure cases in dogs: degenerative mitral valve disease (about 75 to 80% of cases) and dilated cardiomyopathy (about 20% of cases).
Mitral valve disease (MVD) affects the valve between the left atrium and ventricle: it gradually deteriorates with age, allowing blood to leak backward, and eventually overloads the heart. It mainly affects small breeds over 6-7 years old. The Cavalier King Charles is by far the breed most affected by MVD, with nearly a 100% risk of developing the disease in their lifetime.
Dilated cardiomyopathy (DCM) is different: it is the heart muscle itself that weakens and thins, reducing its ability to contract effectively. It mainly affects large breeds, with the Doberman as the most documented case (more than one in two Dobermans during their lifetime).
Other rarer causes exist (congenital malformations, arrhythmias, cardiomyopathies secondary to another pathology), but these two diseases account for the vast majority of heart failure diagnoses in dogs.
Symptoms of heart failure in dogs: signs to watch for #
Symptoms progress in stages, from the most subtle to the most severe — spotting them early, even isolated, warrants a veterinary consultation rather than waiting for them to worsen.
| Stage of appearance | Symptoms |
|---|---|
| Early signs, often overlooked | Occasional cough at rest or upon waking, shortness of breath after previously well-tolerated exertion, slight decrease in endurance, slightly faster breathing during sleep |
| More pronounced signs | Frequent cough including at night, noticeable fatigue, loss of appetite, rapid and labored breathing even at rest |
| Advanced signs / emergency | Swollen belly (ascites), pale or bluish gums, syncope (brief loss of consciousness), weight loss and muscle wasting, respiratory distress |
Any one of these signs, especially if new or persistent, warrants a consultation — no need to wait for them to accumulate. Nighttime cough and shortness of breath at rest are the two most commonly reported signals before a heart failure diagnosis.
Stages of heart failure in dogs (ACVIM classification) #
Veterinary cardiology uses a 5-stage classification (A to D), established by the American College of Veterinary Internal Medicine (ACVIM), which clearly distinguishes risk, silent disease, and declared heart failure.
| Stage | Definition | Visible symptoms |
|---|---|---|
| A | Dog at risk (predisposed breed, age), normal heart on examination | None |
| B1 | Heart murmur detected on auscultation, heart size still normal | None |
| B2 | Heart murmur + dilated heart (visible on echocardiography/radiography) | None, but the risk of progressing to heart failure in the short term increases significantly |
| C | Declared congestive heart failure | Cough, shortness of breath, fatigue, ascites |
| D | Heart failure refractory to standard treatment | Severe symptoms despite treatment |
Stage B2 is the most strategic: the dog still shows no visible symptoms, but the veterinary examination (murmur + cardiomegaly) already indicates that the disease has crossed a critical threshold. It is precisely at this stage that early treatment makes the greatest difference — see the next section.
Why early detection really makes a difference #
A landmark study in veterinary cardiology, the EPIC study (Boswood et al., 2016, Journal of Veterinary Internal Medicine, 354 dogs), demonstrated that treatment with pimobendan started at stage B2 — before the appearance of any symptoms — delayed the onset of congestive heart failure by a median duration of about 15 months compared to a placebo. Concretely, dogs treated from stage B2 reached the disease progression criterion after a median of 1228 days (about 41 months), compared to 766 days (about 25.5 months) for untreated dogs at this stage.
This study clearly illustrates the central issue around heart failure: the most effective window of action is before symptoms, at a time when only regular veterinary examinations (auscultation, then echocardiography if a murmur is detected) or close monitoring at home can reveal that something is evolving.
How to monitor your dog’s respiratory rate at home #
Monitoring the resting or sleeping respiratory rate is the most recommended home monitoring tool by veterinary cardiologists to detect cardiac decompensation before the appearance of visible symptoms. Veterinary cardiologists recommend daily monitoring of this rate in dogs already being monitored for heart disease, especially under diuretic treatment: a resting respiratory rate that gradually increases, even before crossing the threshold of 30 movements per minute, can signal ongoing cardiac decompensation, even before cough or shortness of breath become noticeable to the naked eye.
In practice, the manual method involves counting the chest movements for 30 seconds (dog asleep or at complete rest), then multiplying this number by two. A resting respiratory rate consistently above 30 movements per minute is considered abnormal and warrants contact with your veterinarian.
It’s a useful exercise, but difficult to do regularly on a daily basis — hence the interest in automated monitoring. The Biotracker continuously measures your dog’s respiratory rate, day and night, with an accuracy validated at 98.6% compared to manual counting in the context of the AI-COLLAR study (peer-reviewed research, published in Frontiers in Veterinary Science, 703 dogs in 29 countries). For a dog already diagnosed or at risk (predisposed breed, heart murmur detected at stage B1/B2), this continuous monitoring advantageously replaces occasional manual counting — and allows, via the Biotrack platform, to share this data directly with the veterinarian, who receives AI-sorted alerts in case of significant deviation from the dog’s reference values.
Which breeds are most at risk? #
The predisposed breeds are not the same depending on the heart disease involved.
| Disease | Most affected breeds |
|---|---|
| Mitral valve disease (MVD) | Cavalier King Charles, Yorkshire, Brittany Spaniel, Cocker, Dachshund, Poodle |
| Dilated cardiomyopathy (DCM) | Doberman, Boxer, Great Dane, Golden Retriever, Labrador, Rottweiler, Irish Setter, Dalmatian, Newfoundland, Saint Bernard |
In both cases, the risk increases significantly from 6-9 years old, with clinical signs most often appearing between 7 and 8 years old in small breeds predisposed to MVD.
Veterinary diagnosis: what tests, and when to consult? #
A heart murmur detected during routine auscultation is often the first signal, well before the appearance of any symptoms — which is why regular veterinary check-ups remain essential, even in a dog that seems in perfect health, especially for predisposed breeds from 5-6 years old.
If a murmur or doubt is detected, additional tests generally include:
- a chest X-ray, to assess heart size (cardiomegaly) and lung condition;
- an echocardiogram, the reference examination to confirm and precisely stage the disease (B1 vs B2 in particular);
- an electrocardiogram (ECG), especially in case of suspected arrhythmia or dilated cardiomyopathy;
- blood and urine tests, sometimes including a cardiac biomarker assay (NT-proBNP).
Consult without delay if your dog coughs at rest or during sleep, experiences abnormal shortness of breath, shows new decreased endurance, or has abdominal swelling — these are the signals that, in clinical practice, most often precede a diagnosis of declared congestive heart failure.
FAQ #
Can a dog with heart failure still live long? #
Yes, especially if the disease is detected at an early stage (B1/B2) and monitored regularly. With appropriate treatment started early, the EPIC study showed a median extension of 15 months before the onset of congestive heart failure itself — and once declared, well-adjusted treatment (triple therapy: diuretic, pimobendan, ACE inhibitor) often maintains a good quality of life for several months to a few years, depending on the cause and severity.
What is the difference between a heart murmur and heart failure? #
A heart murmur is an abnormal sound detected during auscultation, indicating a valve leak or disturbed blood flow — it often corresponds to stages B1/B2, without visible symptoms. Heart failure (stage C) occurs later, when the heart can no longer compensate and fluid accumulates in the lungs or abdomen, causing concrete symptoms (cough, shortness of breath, fatigue).
Is a cough always a sign of heart problems in dogs? #
No — a cough in dogs can have many causes (trachea, airways, allergies, lung parasites). But a cough that occurs at rest or during sleep, without prior effort or excitement, is a signal more specifically associated with a heart problem and warrants a consultation, especially in a predisposed breed or senior dog.
How do I know if my dog is at risk of heart failure? #
The main risk factor is breed: small breeds (Cavalier King Charles, Yorkshire, Dachshund…) are mainly exposed to mitral valve disease, large breeds (Doberman, Boxer, Great Dane…) to dilated cardiomyopathy. Age (from 6-7 years) is the second main factor. An annual veterinary check-up with cardiac auscultation remains the best way to detect a murmur before any symptoms.
What is a normal respiratory rate for a dog at rest? #
A resting or sleeping respiratory rate below 30 movements per minute is considered normal in most adult dogs. Consistently above this threshold, or in case of gradual increase (for example from 25 to 35 movements per minute), contact with your veterinarian is recommended, as this may signal the onset of cardiac decompensation.
Can the Biotracker replace veterinary monitoring for a cardiac dog? #
No, and that is not its purpose: the Biotracker continuously measures heart and respiratory rates and can alert in case of deviation from your dog’s reference values, but it does not make a diagnosis. It complements — never replaces — regular veterinary monitoring, providing the veterinarian with objective and continuous data between consultations, notably via the Biotrack platform.
Verdict: early detection remains the best weapon #
Heart failure in dogs progresses silently for months, sometimes years, before the first visible symptoms — and it is precisely during this silent period that treatments are most effective, as shown by the EPIC study. Between regular veterinary check-ups and continuous home respiratory rate monitoring thanks to the Biotracker, you give your dog and their veterinarian the best chance to spot a problem before it becomes visible — and therefore urgent.