Ventricular arrhythmia
Irregularities in the rhythm of contraction of the ventricles of the heart are some of the commonest cardiac arrhythmias seen in dogs. In most cases there is either a structural abnormality within the heart such as the change in cardiac muscle structure which occurs in cardiomyopathy, or there is a systemic problem affecting the heart's performance (e.g. septicaemia).

Age of onset
The irregular ventricular heart rhythm is usually detected during routine physical examination in young dogs 4-12 months of age.

Sex
Males and females are both equally likely to be affected.

History
There is usually no history of feinting or exercise intolerance. Most dogs are outwardly normal before they die suddenly.

Death most often occurs between 4-8 months of age, and often occurs during sleep or during a resting period after exercise.

ECG abnormalities
ECG and Holter monitoring findings vary from one dog to another. A few supraventricular premature complexes, frequent ventricular bigeminy, ventricular couplets and periods of ventricular tachycardia have all been reported.

Inheritance
Genetic inheritance has been confirmed from analyses of pedigrees, but the precise mechanism has not been confirmed.

Postmortem examination
Routine post-mortem examination has failed to confirm the final cause of death or the underlying cause. It is assumed that the dogs die eventually from ventricular fibrillation.

Treatment
50% of the dogs with increased ventricular contraction rate (tachycardia) will die suddenly within the first year of life.

Intravenous antiarrhythmic drugs (lidocaine and procainamide) are effective drugs for controlling arrhythmias and are recommended in these dogs, but more studies need to be performed.

Breeding
Breeding from lines of affected dogs is not recommended.

A chapter on this disease was published in Kirk's Current Veterinary Therapy XI in 1992. To order the latest XIII edition (1999)