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.

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Types of Heart Disease in Dogs

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.