Inherited arrhythmia leading to sudden deaths in young Finnish Leonbergers under investigation

Inherited malignant ventricular arrhythmia is a fairly common disorder among Finnish Leonbergers under three years of age, with the most severe cases potentially resulting in sudden death. Researchers are striving to identify the gene mutation underlying the disorder.

A new study in Finland has revealed that inherited malignant ventricular arrhythmia is fairly common among Finnish Leonbergers under three years of age. At its worst, such arrhythmia can result in the dog’s sudden death.

Arrhythmia and sudden death in Leonbergers have been a subject of research coordinated by Professor Hannes Lohi since 2016 at the Faculty of Veterinary Medicine, University of Helsinki, the University’s Veterinary Teaching Hospital and the Finnish Food Authority.

A total of 46 Leonbergers were enrolled for comprehensive cardiac examinations, of whom 15 per cent were diagnosed with severe arrhythmia and  another 15 per cent with milder cardiac changes. In addition, the project involved 21 Leonbergers that had died suddenly before turning three, and who had had a postmortem evaluation performed on them.

“No changes indicative of any other causes of death were identified in the evaluations, which makes cardiac arrhythmia the most likely cause of the sudden deaths,” says Maria Wiberg, docent of small animal internal medicine at the Veterinary Teaching Hospital, who coordinated the clinical examinations.

Arrhythmia in dogs comes in varying degrees of severity. Diagnosing ventricular arrhythmia does not necessarily mean that the dog will perish, although the risk of sudden death does increase. For example, in a study previously carried out in the United States on German Shepherd dogs, it was found that arrhythmias may become less frequent as the dog grows older. The severity of the disorder also varies from day to day.

Arrhythmia is inherited, but the hunt for the relevant genes continues

In the Finnish study, the model of inheritance for arrhythmias was assessed on the basis of family connections between the dogs that had died suddenly and those suffering from arrhythmia.

Arrhythmia is common in Leonbergers, and the disorder typically occurs in littermates, making it likely that the factors underlying it are hereditary. Unfortunately, in the clinical study, it was not possible to perform cardiac examinations on the affected dogs’ parents when they were under the age of three. Thus, the precise model of inheritance is yet to be determined. For dogs whose heart has been examined at more than three years of age, the findings do not necessarily reflect the cardiac health in the dog's youth.

“We are in the process of carrying out a variety of DNA analyses to identify the arrhythmia gene, a finding that would facilitate disease diagnostics. Furthermore, it would help compare findings to arrhythmia in humans, potentially increasing understanding of the biological causes of arrhythmias. This would boost early diagnostics, breeding programmes and, potentially, the development of drug therapies. Ventricular tachycardia is also a significant and, to a considerable degree, unsolved problem in human medicine,” says Professor Hannes Lohi.

The canine biobank of the University of Helsinki holds DNA samples from over 600 Leonbergers. However, the research group is looking for more blood samples to have as many as possible at their disposal, also in cases of sudden death.


Wiberg M, Niskanen J, Hytönen MK, Dillard K, Hager K, Anttila M, Lohi H. Ventricular arrhythmia and sudden cardiac death in young Leonbergers. J Vet Cardiol 2020; 27:10-22. doi:10.1016/j.jvc.2019.11.006