Sudden Death in Borzoi

The information below was collected from various writings by Nancy Hopkins

[What we know]
What we have seen so far with regards to what seems to trigger the arrhythmias that cause sudden death: Sudden deaths happen often after heavy exercise as the heart rate is dropping and coming back to normal. Borzoi have also dropped dead during excitement such as seeing something on the other side of the fence, watching squirrels and trying to get them, bouncing up and down at the fence. Borzoi have also died in their sleep. We have seen runs of arrhythmias when the borzoi was under emotional stress.

Of course, there can be other things that can cause sudden death than cardiac issues. This is why it is so important to do a necropsy.

A sudden death where nothing definitive is found, and the heart appears normal, is the hallmark of a sudden cardiac death caused by an arrhythmia.
Early stage cardiomyopathies can cause arrhythmias that potentially lead to sudden death. There are also channelopathies that can cause sudden death. In humans, they do molecular necropsies on these hearts. This type of necropsy is not available to veterinary patients apparently.

[What we don’t know]

What we do not yet know is that if every borzoi that has arrhythmias will eventually develop structural changes in the heart, and how those changes will manifest and develop over time. We do not have a way to predict which dogs may be carriers or clear, or if this is even a simple recessive.

Studies

[holter study]
[TAMU echo study]
[heart necropsy study]
[Anything we have learned, study progress, etc]
[encourage participation]

Holter Testing

A holter test is an electric reading of the heart. This typically takes place over 24 hours.
[link to bcoa holter study/rental program]
[link to bhwf holter rental program]
[example of holter results]
[explanation of various terms, example of what a VPC looks like, etc]

Is it true that borzoi who have had good looking holters, even perfect, have dropped dead? Yes. However, the question is, had these dogs been holtered just prior to their death , what would we have seen? In the case of one dog (B), two littermates that had been holtered near immediately after the tragedy, now show considerably higher levels of arrhythmias, and one with additional concerning complexities. Both of these dogs had never had a holter that would arouse suspicion based on the Large Breed Guidelines [<— link] for holter interpretation. Now they do.

What this tells us is that things are in the process of changing for the worse in the hearts of these dogs. This is the nature of a late onset disease. However, as exhibited by the tragic death of dog B’s young daughter at 14 months of age, as well as other young borzoi who have died from sudden death, this disease can develop early in life. These findings punctuate the absolute need for repeat cardiac screenings throughout a breeding animal’s life. Their hearts will appear normal until they are not.

The arrhythmias that are killing these dogs apparently occur only sporadically or under specific circumstances. So the best way to catch these on a holter is when the dog is doing something of the nature above. The dog definitely needs to be able to engage in vigorous exercise and also needs to be able to have a deep sleep during a holter exam.

Borzoi are not dobermans, but the European Society of Veterinary Cardiologists Holter guidelines developed for dobermans for screening their form of dilated cardiomyopathy (DCM) is helpful.

Less than 50 ventricular premature beats (VPCs) are considered normal. However, they add that any VPCs are concerning. 50-300 VPCs is a grey area and requires a repeat holter in 6 months. If 2 holters show 50-300 VPCs within a year, then the dog is diagnosed as being positive for doberman DCM, even if the echocardiogram is normal. Greater than 300 VPCs is considered diagnostic for doberman DCM, even if the echo is normal. While what is going on with borzoi hearts is not the same as doberman DCM, it is similar in that it appears to have both an arrhythmia aspect and a structural aspect. So far, it appears the rhythm disturbances precede the structural changes in our breed, so a borzoi can be affected while showing normal heart structure and function on an echocardiogram.

Breeding

It is imperative, when looking for outside dogs or bitches for your lines, to make sure they have had as recent an echocardiogram and holter screening as possible before you agree to a breeding. It is exceedingly important to take great care to prevent breeding two dogs who have had sudden death [at least] close up in their pedigrees. When breedings like this have occurred, the risk of sudden death appears to increase. That isn’t to say that dogs with 1st degree relatives with sudden death should not be bred. Based on statistics, in a litter with first degree relatives that have dropped dead, there is a very high probability that not every dog or bitch in that litter will be affected. Breed any animals that have 1st degree relatives with SD carefully so that you do not double up on this heart disease.

It must be stressed that we cannot eliminate entire pedigrees.

Also, remember that while we do not yet know what a normal holter is in borzoi, holter results that would be abnormal in any dog is definitely abnormal in a borzoi. Such animals should not be bred.