The inherited condition -- called subvalvular aortic stenosis (SAS) -- also affects children and other dog breeds. Surgery can correct the problem in children, but not in dogs, the researchers noted.
In dogs, SAS shows up in the heart as a ridge or ring of abnormal tissue growth below the aortic valve that restricts blood flow from the heart into the aorta. The condition can cause fainting, sudden collapse, irregular heart rate or sudden death.
Dogs with mild SAS can have a normal lifespan, but those with the severe form are likely to die before they are 4.5 years old, even if they receive medications.
The researchers identified the gene mutation associated with canine SAS after analyzing thousands of genes in Newfoundland dogs. The mutation occurs in a gene called PICALM, according to the study published recently in the journal Human Genetics.
The same gene mutation has been linked to the formation of plaque-like lesions in the brains of people with Alzheimer's disease, according to study leader Dr. Joshua Stern, a veterinary cardiologist at the University of California, Davis.
"Our hope now is that breeders will be able to make informed breeding decisions and avoid breeding dogs that harbor this mutation, thus gradually eliminating the disease from the Newfoundland breed," Stern said in a university news release.
"In addition, now that we know one gene is responsible for SAS and more about which proteins are involved, we can move forward to consider novel therapies that may help treat this devastating condition," he added.
The U.S. National Library of Medicine has more about congenital heart defects in people.