Heart Disease in Dogs: Symptoms, Types, and the Breed Risks You Need to Know

9 min read |

Heart disease in dogs is more common than most owners realise, and more manageable than most people fear. PetMD defines it as any condition that affects the heart’s ability to pump blood effectively — valve disease, heart muscle disorders, arrhythmias, or heartworm infection. Early signs may be subtle, the condition can progress to congestive heart failure if undetected, but diagnosis and ongoing management with medication and lifestyle adjustments can significantly extend a dog’s comfortable life.

Dogs cannot tell us their chest hurts or that they feel breathless after less exercise than usual. Heart disease progresses silently in many dogs for months or years before it becomes obvious. By the time a dog presents with obvious breathing difficulty or collapse, the condition is typically well advanced. This is why regular veterinary check-ups including cardiac auscultation matter so much, particularly for breeds at elevated risk.

This guide covers the types of heart disease, the symptoms at different stages, the breed-specific risks that should prompt proactive monitoring, the grain-free diet controversy, and the treatments that genuinely make a difference.

You may also want to read our guide on signs a dog is in pain.

Related: our guide on why is my dog lethargic? covers this in more depth.

Types of Heart Disease in Dogs

This post is part of our complete pet health library — visit our pet health guide for the full collection.

Condition	Most affected breeds	Key distinction
Mitral valve disease (MVD)	Cavalier King Charles Spaniels, small breeds, older dogs	Most common heart disease in dogs — the valve degenerates and leaks
Dilated cardiomyopathy (DCM)	Dobermans, Great Danes, Irish Wolfhounds, Boxers, Golden Retrievers	Heart muscle weakens and enlarges — most common in large breeds
Arrhythmias	Boxers (ARVC), any breed	Abnormal electrical rhythms — can cause sudden collapse or death
Pericardial disease	Golden Retrievers, German Shepherds, large breeds	Fluid around the heart — causes tamponade (compression) of heart
Congenital defects	Any breed — some hereditary	Present from birth — caught on puppy examination

Mitral Valve Disease — The Most Common Type

Mitral valve disease (MVD) is the most common form of heart disease in dogs overall, particularly in small and medium breeds over 5 years old. The mitral valve, which controls blood flow between the left atrium and ventricle, degenerates and begins to leak — the heart compensates by working harder, gradually enlarging, until it can no longer maintain adequate circulation.

Cavalier King Charles Spaniels have such a high prevalence of MVD that responsible breeders screen for it using cardiac auscultation and echocardiography, and breeding guidelines in many countries recommend against breeding affected dogs. By age 10, nearly all Cavalier King Charles Spaniels have a heart murmur. This is not a death sentence with early detection and management.

Most dogs with a heart murmur from MVD live comfortable lives for years before progression to symptomatic heart failure. The landmark EPIC study showed that pimobendan given to dogs with preclinical MVD significantly delays the onset of heart failure.

Dilated Cardiomyopathy (DCM) — The Large Breed Threat

DCM is the second most common heart disease in dogs and is the leading cardiac cause of death in large and giant breeds. Vetster describes the mechanism: the heart muscle weakens and stretches, losing its ability to pump blood effectively. Blood buildup causes further weakening and stretching, eventually leading to congestive heart failure.

The most important feature of DCM clinically: most dogs are asymptomatic until they are already in congestive heart failure or develop a dangerous arrhythmia. Daily Paws notes this directly: because DCM is not easily detectable early on, it is usually not diagnosed until signs of CHF are present.

Sudden death can be the first sign of disease in some Dobermans — a reality that makes proactive screening for at-risk breeds critically important.

Breed-Specific Risks — Know Whether Your Dog Needs Proactive Screening

These breeds warrant regular cardiac assessment even without symptoms — annual auscultation by a vet and echocardiography as recommended by breed health guidelines:

• Doberman Pinschers— highest DCM risk of any breed. Up to 58% develop DCM by age 8 in some studies. Annual echocardiography recommended from age 2 to 3.
• Great Danes— very high DCM prevalence. Often diagnosed later than Dobermans due to less systematic screening.
• Irish Wolfhounds— DCM combined with arrhythmias. Significantly shortened lifespan due to cardiac disease.
• Boxers— ARVC (arrhythmogenic right ventricular cardiomyopathy) rather than DCM. Can cause sudden death.
• Cavalier King Charles Spaniels— MVD in virtually all dogs by age 10. Most studied and best managed with breed-specific protocols.
• Golden Retrievers— DCM and pericardial effusion. Rising concern, particularly related to the grain-free diet investigation.

The Grain-Free Diet and DCM — The Controversy Explained

In 2018, the FDA began investigating a potential link between grain-free diets and DCM in dogs — specifically diets high in peas, lentils, chickpeas, and potatoes as grain substitutes. The reports clustered unusually in breeds not typically predisposed to DCM, including Golden Retrievers.

The investigation has not definitively established causation. VetLens’ 2026 cardiomyopathy guide notes that DCM in dogs has multifactorial causes including genetic inheritance, diet, toxins, metabolic conditions, and infectious disease. However, the FDA advisory and subsequent veterinary nutrition guidance has led most board-certified veterinary cardiologists to recommend caution with grain-free diets — particularly for breeds at elevated risk.

The practical recommendation from most veterinary cardiologists: choose a dog food that uses grains rather than legumes and pulses as carbohydrate sources, from a manufacturer that conducts AAFCO feeding trials and employs veterinary nutritionists. If your dog is on a grain-free diet and belongs to an at-risk breed, discuss this with your vet.

Symptoms — What Heart Disease Looks Like

Early stage — often subtle or absent

Exercise intolerance — tiring faster on walks, reluctance to run or play. Occasional cough, particularly at night or after excitement. Slight breathing changes. A vet may detect a heart murmur on routine examination before the dog shows any symptoms at home.

Moderate stage — more obvious

PetMD identifies the progressive symptoms: persistent cough, rapid or laboured breathing even at rest, reduced appetite and weight loss, lethargy, and weakness. The abdomen may begin to distend as fluid accumulates. The dog may sleep in a head-elevated position to ease breathing.

Congestive heart failure — emergency signs

Difficulty breathing at rest, blue-tinged gums (cyanosis indicating oxygen deprivation), complete collapse, inability to stand. These require emergency veterinary care. VCA Animal Hospitals notes that liver and kidney function are often impaired in heart disease — regular blood and urine testing is part of monitoring.

Treatment — What Actually Helps

Pimobendan — the most important medication

Davies Veterinary Specialists confirms the key clinical role of pimobendan: once the heart enlarges, treatment with pimobendan has been shown to delay the onset of heart failure in dogs with DCM. For MVD, the EPIC study showed the same benefit in preclinical disease. Pimobendan strengthens heart muscle contraction and dilates blood vessels, reducing the work the heart must do.

Diuretics

Furosemide and spironolactone are used to remove excess fluid that accumulates in congestive heart failure — from the lungs (causing the cough and breathing difficulty) and from the abdomen. Regular monitoring of kidney values is essential as diuretics increase renal workload.

ACE inhibitors

Enalapril and benazepril reduce the pressure the heart pumps against, easing the load on a failing heart. Used alongside pimobendan and diuretics as part of the standard heart failure medication protocol.

Lifestyle modifications

Controlled, gentle daily exercise — not complete rest, as muscle mass and circulation benefit from gentle activity, but no high-intensity exercise. Low-sodium diet reduces fluid retention. Ramps instead of stairs reduce exertion. Regular weight monitoring helps detect fluid accumulation early.

Frequently Asked Questions

Q: My dog has been diagnosed with a heart murmur — how serious is this?A: A heart murmur is graded 1 to 6, with higher grades indicating more significant turbulence. Murmurs exist on a spectrum — a Grade 1 or 2 murmur in an otherwise healthy dog may be monitored without treatment for years. A Grade 5 or 6 murmur in a symptomatic dog is a different situation entirely. Your vet will grade the murmur and recommend echocardiography if it warrants further investigation. A murmur diagnosis alone does not mean heart failure is imminent.

Q: How long can a dog live with heart disease?A: With appropriate management, many dogs live comfortably for 1 to 3 years after a heart failure diagnosis. Some live longer. Quality of life rather than survival duration is often the more meaningful metric — well-managed heart failure patients can maintain a genuinely good quality of life for extended periods. The key variables are stage at diagnosis, breed, specific condition, and medication response.

Q: Can heart disease in dogs be prevented?A: Not completely, as genetic predisposition plays a major role. However: maintaining healthy weight (which reduces cardiac workload), year-round heartworm prevention (to prevent heartworm disease), avoiding grain-free diets for at-risk breeds, and regular veterinary screening for at-risk breeds all reduce risk or enable earlier intervention. For Cavalier King Charles Spaniels, choosing a breeder who follows the breed cardiac protocol significantly reduces the probability of early-onset MVD.

Frequently Asked Questions About Heart Disease in Dogs

What are the first signs of heart disease in dogs? The earliest signs of heart disease in dogs are often subtle and easy to miss. Owners may notice their dog tiring more quickly on walks, coughing (especially at night or after lying down), breathing faster than usual during rest, or showing reduced enthusiasm for play. A persistent soft cough is one of the most common early indicators of heart disease in dogs, as fluid can build up in the lungs when the heart is not pumping efficiently. Any of these signs warrants a prompt vet check including a stethoscope exam and possibly chest X-rays.

Which dog breeds are most at risk of heart disease in dogs? Certain breeds carry a significantly higher genetic predisposition. Cavalier King Charles Spaniels are the most well-known example — nearly all develop mitral valve disease by age 10. Doberman Pinschers are particularly prone to dilated cardiomyopathy (DCM), a serious form of heart disease in dogs that enlarges and weakens the heart muscle. Other breeds at elevated risk include Boxers, Great Danes, Irish Wolfhounds, and Cocker Spaniels. If your dog belongs to a high-risk breed, annual cardiac screenings from middle age are strongly recommended.

How is heart disease in dogs treated? Treatment depends on the type and stage of the disease. Mitral valve disease — the most common form of heart disease in dogs — is managed with medications such as pimobendan, ACE inhibitors, and diuretics to reduce fluid build-up and support heart function. Dilated cardiomyopathy may also be treated with taurine supplementation in some cases. While there is no cure, the right combination of medication, controlled exercise, and a low-sodium diet can significantly extend a dog’s quality of life and slow disease progression.

Can diet help manage heart disease in dogs? Yes — diet plays an important supporting role. Dogs with heart disease in dogs are often prescribed a low-sodium diet to reduce fluid retention and ease the heart’s workload. It is also worth discussing taurine and L-carnitine levels with your vet, as deficiencies in these amino acids have been linked to certain forms of DCM, particularly in large breeds eating grain-free diets. Always consult your vet before changing your dog’s diet, as the right approach varies based on the specific type and stage of the condition.

If you want to dig deeper, check out our guide on why is my dog not eating?.

Medical Disclaimer This article is written for informational purposes based on the research and personal experience of the author. It is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult your veterinarian with concerns about your pet’s health.

This article is written for informational purposes and reflects the personal experience and research of the author. It does not replace professional veterinary or dog training advice. Always consult your veterinarian or a certified trainer for individual guidance.