Health
What is the main cardiac condition in Newfoundlands?
Subaortic stenosis, a congenital narrowing below the aortic valve. It is present from birth, often first detected as a puppy murmur, and its severity varies from trivial to life-limiting.
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Newfoundland Cardiac Disease: The Murmur You Must Not Let Go
Quick answer
What is the main cardiac condition in Newfoundlands?
Subaortic stenosis, a congenital narrowing below the aortic valve. It is present from birth, often first detected as a puppy murmur, and its severity varies from trivial to life-limiting.
Subaortic stenosis is a narrowing below the aortic valve. It produces a murmur, it is often first heard between six and sixteen weeks, and in its severe form it can kill a young dog who has never shown a symptom.
This page is for anyone whose Newfoundland puppy has had a murmur noted, anyone choosing a breeder and trying to understand what cardiac clearance actually means, and anyone whose adult dog has just been found to have a heart abnormality.
Important reminder
This guide is not medical advice. If your dog shows pain, sudden behavior change, or worsening symptoms, consult a licensed veterinarian.
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What this problem looks like
Cardiac disease in the Newfoundland comes in two documented forms with opposite characters. Subaortic stenosis is congenital, present at birth, detected as a murmur in puppyhood, and dangerous in proportion to how narrow the outflow is. Dilated cardiomyopathy is acquired, arrives in adulthood, and has a long silent phase. Both can cause exertional fainting and sudden death, and both are reasons why this breed's heart deserves attention at every life stage rather than only in old age.
Common triggers
- A murmur detected at a puppy vaccination or pre-operative examination
- Exertion or excitement, when oxygen demand exceeds what a restricted outflow can supply
- Anaesthesia, which alters blood pressure and cardiac output
- Age, in the case of acquired heart muscle disease
- A pedigree containing dogs that died suddenly or unexpectedly young
Subaortic stenosis is one of the more frequently encountered congenital heart defects in large breeds, and it sits explicitly on the Newfoundland's list of common health issues alongside dilated cardiomyopathy, hip dysplasia, cystinuria and bloat. Most Newfoundlands do not have significant cardiac disease. The reason the breed is screened so carefully is that the severe form of the condition can kill a young, apparently healthy dog without warning, and screening is the only way to identify it.
Why this happens
Breed factors
Subaortic stenosis is inherited and is one of the two cardiac conditions specifically documented for the Newfoundland, which is the whole reason breed clubs place such emphasis on cardiologist examination before breeding. The lesion develops in the weeks after birth, which is why examination timing matters and why a murmur heard at eight weeks may change by sixteen. Body size contributes indirectly: a heart supplying 100 to 150 pounds of tissue is already doing substantial work, and a fixed obstruction leaves less reserve. A lifespan of nine to ten years also means acquired heart disease arrives sooner than in a small breed.
Environment factors
Nothing an owner does causes congenital heart disease. What the environment changes is when problems surface. Intense exertion is the classic unmasking event, and in this breed swimming is more demanding than owners assume. Heat compounds it, since a dog wearing a heavy water-resistant double coat has to move a great deal of air to cool, and that raises cardiac work. Excess body weight increases the load on every heartbeat. And a household that never has the heart formally assessed, relying on the dog looking well, is the single most consequential environmental factor of all.
What you can do at home (once it is not an emergency)
When to talk to your vet
Arrange a cardiology assessment promptly for any murmur in a Newfoundland puppy, and before any elective anaesthetic in a dog with a known murmur. Book urgently for exercise intolerance that is new, coughing at rest, a resting sleeping breathing rate that has climbed and stayed up, or an abdomen that has become distended. Go to an emergency clinic immediately for fainting or collapse, for breathing that is laboured at rest or a dog who refuses to lie down, for gums that are pale, grey or blue, for coughing that produces froth, or for sudden weakness with a fast or chaotic pulse. Collapse in a Newfoundland is never a wait-and-see event, because the two conditions this breed carries can both cause sudden cardiac death.
At home, alongside your vet's plan
- Ask at every appointment whether a murmur was heard, and make sure the answer, including a negative, is written in the record.
- If a murmur exists, ask for a cardiologist referral rather than accepting a plan to recheck in six months.
- Learn to count your dog's breathing rate while they sleep and log it weekly, since a rising trend is a genuine early warning.
- Keep your dog lean, which reduces cardiac workload and improves every other aspect of giant-breed health.
- Exercise in cool conditions and stop before the dog is tired, particularly while any cardiac question is unresolved.
- Film any episode of weakness, wobbling or collapse, because a video is worth more to a cardiologist than any description.
- Carry a copy of any cardiac report to every appointment, including dentals and imaging, since it changes anaesthetic planning.
More Newfoundland health & behavior issues
- Newfoundland ARVC: Is It a Real Risk, and What Causes Fainting?
- Newfoundland Heart Conditions: Screening & Warning Signs
- Newfoundland Heart Disease: Living With the Diagnosis
- Newfoundland Kidney Disease: Early Signs and Monitoring
- Newfoundland Kidney Stones: Cystinuria and Urinary Blockage
- Newfoundland Pancreatitis and Diabetes: The Senior Link
- Newfoundland Pancreatitis: Signs, Triggers and Bloat Confusion
- Newfoundland Allergic Reactions: Swelling, Hives & When to Rush In
- Newfoundland Brachycephalic Features: A Big Head Is Not a Flat Face
- Newfoundland Cherry Eye: Prolapsed Third Eyelid Gland Explained
- Newfoundland Eye Injuries: A Water Dog's Real Risk of Trauma
- Newfoundland Hip Dysplasia Prevalence: Reading the Numbers
- Newfoundland Obesity: Weight Control in a Giant Breed
- Newfoundland Patellar Luxation: Grades and the Differential
- Newfoundland Separation Anxiety: What Owners Actually Pay
Cardiac Disease in other breeds
- Jack Russell Terrier Cardiac Disease: Signs & What to Do
- Labradoodle Cardiac Disease: Signs, Causes & What to Do
- Maltese Cardiac Disease: Signs, Causes & What to Do
- Miniature Schnauzer Cardiac Disease: Signs & What to Do
- Poodle Cardiac Disease: Signs, Causes & What to Do
- Rottweiler Cardiac Disease: Signs, Causes & What to Do
- Standard Schnauzer Cardiac Disease: Signs & What to Do
- Yorkshire Terrier Cardiac Disease: Signs & What to Do
- Akita Cardiac Disease: A Screening-First Overview
- American Pit Bull Terrier Cardiac Disease: Signs
See all Newfoundland health problems, which breeds are prone to cardiac disease, or the full Newfoundland breed guide for temperament, exercise needs and ownership costs.
What to expect, and how you know it is working
An echocardiogram usually answers the question in one appointment. For a puppy with a murmur, cardiologists often want to reassess after the first year, since the lesion can progress during growth. A mildly affected dog is typically reviewed every one to two years and lives a normal life. A severely affected dog is managed with medication and defined limits, monitored more frequently, and the honest expectation is a shortened life with a real risk of sudden death. None of this is curable, and owners deserve to be told that clearly at the first appointment.
Success is knowing. A Newfoundland whose cardiac status has been measured and recorded, whose exercise is calibrated to that measurement, whose anaesthetic plans account for it, and whose owner recognises the warning signs is in a fundamentally better position than an identical dog whose murmur was noted and never followed up. For mildly affected dogs, success is an ordinary life with a diary entry every couple of years. For severely affected dogs, it is stability, comfort and no unexplained crises.
How a Narrow Outflow Damages a Heart
Blood leaves the left ventricle through the aortic valve. In subaortic stenosis a ridge or ring of tissue sits just below that valve, narrowing the exit. The ventricle has to generate much higher pressure to push a normal volume of blood through a smaller opening, and it responds the way any muscle does to sustained overload: it thickens.
That thickening is the problem. A thicker heart muscle needs more blood supply, but the coronary vessels do not expand to match, and the muscle deep in the ventricle wall can become relatively starved of oxygen, particularly during exertion when demand is highest. Oxygen-starved heart muscle is electrically unstable, and that instability is the mechanism behind exertional fainting and sudden death in severely affected dogs.
Severity matters enormously and it varies widely. A dog with mild subaortic stenosis may live a completely normal life with periodic monitoring. A dog with severe disease has a materially different outlook and needs specific management, exercise guidance and cardiological follow-up. The only way to know which you have is an echocardiogram with Doppler measurement, performed by someone who does them regularly.
This is also why a Newfoundland puppy's murmur is not a wait-and-see finding. Some innocent murmurs in puppies do fade by around sixteen weeks. Subaortic stenosis does not, and in a breed where it is a recognised problem, the correct response to a murmur is to find out which kind it is.
What Cardiac Clearance From a Breeder Actually Means
Because this is a congenital and heritable condition, breeder screening is the point at which risk is genuinely reduced. Most buyers do not know what to ask for, and vague reassurances are common.
- Ask who performed the cardiac examination on the parents. An examination by a board-certified veterinary cardiologist carries different weight from one performed by a general practitioner.
- Ask whether the examination was auscultation alone or included an echocardiogram, since a mild lesion can be missed on listening alone.
- Ask for the date. Cardiac status is assessed at a point in time, and a certificate from years earlier tells you less than a recent one.
- Ask about the wider line, not just the parents, and specifically about any dog that died suddenly or unexpectedly young.
- Ask whether the puppies themselves have been examined before going home, and whether any murmurs were found in the litter.
- Ask about hips and elbows in the same conversation, since dysplasia sits alongside cardiac disease at the top of this breed's documented issues.
- Be wary of any breeder who treats these questions as an insult. In this breed they are the standard questions, and good breeders expect them.
The Certificate That Said Very Little: Choosing Fen's Litter
Ivan spent four months looking for a Newfoundland puppy and learned to ask three questions. The first breeder he visited produced a cardiac certificate for the sire dated six years earlier and said the dam had been checked by her own vet and was fine. He asked what fine meant. It meant auscultation in a consulting room, with no echocardiogram. He asked whether any dog in the line had died young. There had been one, at four, described as sudden and unexplained. He left. The breeder he eventually bought from produced echocardiogram reports from a board-certified cardiologist for both parents, dated within the previous eighteen months, and had had the whole litter auscultated at seven weeks with the findings written down for each puppy. Two puppies had soft murmurs noted, and she had told those buyers, which was the detail that convinced him. Fen came home at nine weeks with no murmur. Ivan had him checked again at four months and again before his neuter, and both times the record was written down. He has no cardiac disease, and if he had, Ivan would have known before it mattered. What he says to other buyers is that the questions took ten minutes each and were the only part of the process that could not be undone later.
Key takeaway: In this breed the heart is checked before the dog is bought, not after it collapses. Ask who examined the parents, whether it was an echocardiogram, and when, and never let a puppy murmur go unexplained.
Frequently asked questions
Is heart disease really common in Newfoundlands?
Two of the five conditions most commonly listed for the breed are cardiac: subaortic stenosis and dilated cardiomyopathy. That is unusual and it is why cardiac screening is a standard part of responsible Newfoundland breeding. It does not mean most individual dogs will be affected, but it does mean heart examination should never be skipped.
My puppy has a murmur. Will it go away?
Some soft innocent murmurs in young puppies do resolve by around sixteen weeks. In a Newfoundland you should not assume that. Because subaortic stenosis is a known breed problem and its murmur can sound similar, the appropriate step is an echocardiogram to determine what is causing it rather than a plan to recheck later and hope.
Can subaortic stenosis be cured?
No. It is a structural narrowing present from birth and is managed rather than corrected. Management may include medication in some cases, defined exercise limits, avoidance of high-intensity exertion, careful anaesthetic planning and regular cardiological review. A cardiologist should set the plan based on your dog's measured severity.
Is it safe to exercise a dog with this condition?
That depends entirely on severity, and it is not a judgement to make yourself. Mildly affected dogs often exercise normally. Severely affected dogs are usually advised to avoid intense exertion, because the risk of a dangerous rhythm is highest when oxygen demand peaks. Get written guidance from the cardiologist rather than a general impression.
Should an affected dog be bred from?
This is a heritable condition, and any breeding decision involving a dog with a diagnosed cardiac abnormality should be made with a cardiologist and a breed club rather than independently. The whole purpose of screening is to reduce the frequency of the condition in the next generation.
What signs would tell me the heart is causing problems?
Fainting or collapse during exertion or excitement is the most important. Others include tiring far more quickly than usual, an unwillingness to continue on walks, coughing at rest, laboured breathing, a swollen abdomen, or a resting sleeping breathing rate that has climbed and stayed up. Any of these needs prompt veterinary attention.
Quick answers
View more answersHealth
Should a puppy murmur be investigated?
Yes, with an echocardiogram rather than a recheck-and-hope plan. In a breed where subaortic stenosis is documented, identifying the cause of the murmur is the whole point.
Health
What should I ask a Newfoundland breeder?
Who examined the parents' hearts, whether an echocardiogram was included, when it was done, and whether any dog in the line died suddenly and young. Ask about hips and elbows in the same breath.
Living
How do I monitor a diagnosed dog at home?
Count the resting breathing rate while your dog is asleep, once a week, and record it. A persistent upward trend is one of the earliest home-detectable signs of a heart struggling.
Costs
What does cardiac screening cost?
An echocardiogram with a cardiologist is a significant one-off expense, considerably less than an emergency cardiac workup after a collapse. Many owners of this breed treat it as a necessary part of the first year.
Related DogBreedCompass guides
- dilated cardiomyopathy in Newfoundlands – Dilated cardiomyopathy is the breed's other documented cardiac condition and behaves very differently.
- cardiomyopathy – Heart muscle disease more broadly, including how it is screened and monitored.
- anesthesia and heart disease – Known cardiac disease changes anaesthetic planning for every future procedure.
- collapse during exercise – Exertional collapse has cardiac, heat-related and neurological explanations that must be separated.
- genetic screening in this breed – Breeder screening for heart, hips and inherited disease is best understood together.
Bring the right questions to the vet
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