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.

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.