Newfoundlands and SAS: Heart Disease Risks Explained

Among the largest dog breeds, the Newfoundland is cherished for its gentle temperament and sturdy build. Unfortunately, this impressive breed is susceptible to some serious health issues, including a congenital heart disease known as subvalvular aortic stenosis (SAS). This condition impairs heart function and, if untreated, can drastically shorten a dog’s lifespan.

What Is Subvalvular Aortic Stenosis (SAS)?

SAS is an inherited disorder that involves the narrowing just below the heart’s aortic valve. This constriction arises from fibrous or cartilaginous growths which obstruct blood flow from the left ventricle to the aorta, the artery that distributes oxygenated blood throughout the body. The severity of SAS varies widely, with some dogs experiencing mild symptoms or none at all, while others face serious heart complications or sudden death.

Research in the US has pinpointed a mutation in the PICALM gene strongly linked to SAS in Newfoundlands. Interestingly, this gene is related to one associated with Alzheimer’s disease in humans. SAS passes through autosomal dominant inheritance with incomplete penetrance, meaning not all dogs with the gene show symptoms, but can still pass it to offspring.

How Does SAS Impact Newfoundlands?

SAS disrupts heart valve function and causes turbulent, restricted blood flow, often leading to a detectable heart murmur during veterinary exams. Murmur intensity is graded on a scale from 0 (no murmur) to 6 (very severe). Dogs with mild SAS may live symptom-free, but those with severe cases risk heart failure or sudden collapse, sometimes as young as 4 years.

Diagnosis often requires echocardiography (echo-Doppler) to visualize heart structures. However, unlike in human medicine, surgical options to remove obstructive tissue are rarely used in dogs. Management typically focuses on symptom control and regular monitoring.

Testing for SAS and Responsible Breeding Practices

In the US, genetic screening for the PICALM mutation is available through labs such as the Veterinary Genetics Laboratory at the University of California, Davis. Reputable Newfoundland breeders use this testing to make informed breeding choices, aiming to reduce SAS incidence without diminishing genetic diversity.

Since SAS expresses incomplete penetrance, some puppies may carry the gene without immediate or ever manifesting symptoms, highlighting the importance of ongoing monitoring. Breeders often pair carriers only with clear dogs and test offspring to gradually reduce the occurrence of SAS.

Understanding Heart Murmur Grading in Newfoundlands

Veterinarians grade detected heart murmurs to assess severity. A grade of 0/6 indicates a normal heart, while grades from 1/6 to 6/6 show increasing severity. Cardiologists often conduct echocardiograms for an accurate diagnosis and comprehensive heart function evaluation.

Other Cardiac Conditions Causing Murmurs in Newfoundlands

SAS is a primary cause of murmurs in this breed, but other heart abnormalities can also produce such sounds, including:

• Valve Narrowing: Conditions like pulmonic stenosis restrict blood flow, leading to murmurs.
• Valve Leakage: Regurgitation through mitral or tricuspid valves causes turbulent flow detectable as murmurs.
• Structural Defects: Abnormal shunts such as septal defects allow abnormal blood passage and murmurs.

Specialized cardiac exams and imaging are necessary to determine exact causes.

Conclusion

Subvalvular aortic stenosis represents a serious hereditary heart condition affecting Newfoundlands in the US. With the discovery of the PICALM gene mutation, genetic testing helps breeders responsibly reduce SAS risk while preserving the breed’s genetic health. Early detection via heart murmur screening and specialized cardiac testing enhances disease management and improves quality of life.

Prospective owners should choose puppies from breeders committed to health screening. Current Newfie owners are encouraged to maintain regular veterinary check-ups to monitor their dog’s heart status.

Through informed care and breeding, we respect our responsibility to these majestic dogs, supporting long, healthy, and joyful lives as treasured companions.