Shop our Father's Day Sale—up to




Save Now

Shop our Father's Day Sale—up to




QT Syndrome

Long QT Syndrome (LQTS) is a rare cardiac disease that causes an irregular heart beat and has been associated with sudden death in the English Springer Spaniel.

Key Signs

Prolonged QT interval, Biphasic T-wave, Sudden death

Age of Onset

0 to 2 yrs

Juvenile onset


Autosomal Dominant

For autosomal dominant disorders, dogs with one or two copies of the disease variant are at risk of developing the condition. Inheriting two copies of the risk variant may make the risk higher or the condition more severe. They may produce puppies affected with the disorder if bred.

Likelihood of the Condition

Moderate-high likelihood

At risk dogs are likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with LQTS

Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about LQTS

Affected dogs are presented with an abnormally long QT-interval in the ECG. Affected dogs have no other clinical signs but have a very high tendency for sudden death during activity. Sudden death is most likely due to acute ventricular fibrillation. Some affected dogs may have a systolic murmur or increased heart rate on physical examination and some may show an abnormal biphasic T-wave on ECG. There is no curative treatment for the disease.

Beta blockers and avoidance of strenuous activity and excitement are commonly used for treatment but do not diminish the risk of sudden cardiac death.

For Breeders

Planning to breed a dog with this genetic variant?

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disease is autosomal dominant meaning that one copy of the mutation is needed for disease signs to occur. Use of dogs with one or two copies of the disease mutation for breeding is not recommended, as there is a risk that the resulting litter will contain affected puppies. For example if a dog with one copy of the LQTS mutation is bred with a clear dog with no copies of the LQTS mutation, about half of the puppies will have one copy and half will have no copies of the LQTS mutation. Please note: It is possible that disease signs similar to the ones caused by the LQTS mutation could develop due to a different genetic or clinical cause.

Technical Details

Gene KCNQ1
Variant C>A
Chromosome 18
Coordinate 46,604,412

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Ware, W. A., Reina-Doreste, Y., Stern, J. A., & Meurs, K. M. (2015). Sudden Death Associated with QT Interval Prolongation and KCNQ1 Gene Mutation in a Family of English Springer Spaniels. Journal of Veterinary Internal Medicine, 29(2), 561–568. View the article