It is very likely that there will be a large number of dogs with the mutation in the population. Removal of all mutation positive dogs is NOT recommended. Instead, the information should be used to GUIDE your decisions. This new information should be used IN CONJUNCTION with your other health testing (aortic stenosis Doppler, DM testing, behavior testing,etc) to make the BEST decisions for your line. IT IS NOT INTENDED to be used as a single test to remove or keep a dog in a program.
Dr. Kathryn Meurs, 6/10/2009

These are my rough notes from the webinar held on June 10, 2009 regarding ARVC in Boxers and the new DNA test. They have not been edited for content, spelling, grammar, etc. I do plan to flesh this out shortly and will have a series of Punnet squares up to illustrate the inheritance and various breeding choices.

DCM that Dobermans get is not the same as ARVC. Nor is it the same as ventricular tachycardia in GSDs.

Heart murmurs are not typical of ARVC (are typical of AS).

Echocardiograms are not very important for this disease.

Digital holters - each company has proprietary technology for storing the data, so you need to be sure you have a company that can read the information. Analog monitors can typically be read by any company.

Dog w/80 VPCs, 4 runs of 4 each, tested normal for ARVC. May be a different gene causing ARVC - just because a dog tests negative for this mutation, there may be other genetic causes that lead to the disease. Or, there are other things that can cause VPCs in dogs - viruses even. Doesn't think hypothyroidism is associated with VPCs, but it's possible. Retest the dog in 6 months to a year, if normal wouldn't worry about it. Tumors, old dogs, etc.

0 VPCs in a machine-read tape doesn't mean much unless you know how many total beats were available to be read. Average dog has 90,000-110,000 beats per day. Large number of VPCs in machine-read, certainly have it read by a human. Low numbers with 22-24 hours of readable beats is OK.

In humans there are five genes known to control desmosomes, plus two other genes where mutation will lead to ARVC. In dogs they have only found one gene so far.

Over the next year will be gaining a lot of information. Right now test is just a tool.

Need to look at the test as detecting the presence of this particular mutation, and not as determining whether or not the dog will ever develop ARVC.

With cats, gave updates every 1,000 animals; after the first 1,000 the percentages stayed fairly close. (Is always going to be a little bit biased.)

About 370 test results back; she has not sorted by result yet because of bias. Will probably report when 1,000 dogs are done.

There could very well be a trigger; these things are generally not black and white, single-gene situations.

Homozygous dogs have a higher risk of developing the disease and a higher risk of developing more severe disease, but because of modifiers we don't know yet whether all homozgyous will develop the disease. If great dog, no signs, good holters, end of particular family, breed to negative and carefully selecting replacement puppies for the next generation is acceptable, but her feeling is that because homozygous dogs will with certainty pass on the bad gene this is not recommended in most cases.

Keep sending holter information on tested dogs, it would be very helpful.

Fish oil study - a little cautious, because of the day-to-day variability of VPCs in dogs even without supplementation/treatment (85% variability). Dogs in study did drop, but within range of what could have been variability. However fish oil is very safe and relatively inexpensive; supplementation could help and she would be fine with that.

Can do frozen semen but the process is not fine-tuned yet; recommend holding off on sending semen from limited supply for a bit. Semen should be sent frozen since thawing deteriorates DNA, but doesn't have to be in the container, can be on dry ice.

With swabs, it's important that the swabs are dry before they are put in the sleeves and sent - will last months this way. If not dry mold can form which deteriorates DNA.

Most useful hearts are those taken immediately at the time of death and can be put on dry ice; can coordinate with Dr. Meurs but most vets aren't equipped to do this.

Homozygous/heterozygous, no known affected dogs, longevity in pedigree (lots) that didn't die of cardiac disease. Heterozgyous carefully follow, breed to negative dog, holter generations. Homozygous still very concerned about it.

Populaton for study was pet and show.

If you have a homozygous dog that you know has produced this disease and dogs that have died young, it should not be used. Even if bred to normal. Try to use heterzygous or clear siblings or offspring.

Tails/dewclaws would probably not be useful.

Really not a false positive, as far as presence of the mutation; development of the disease is less certain.

Majority that have it show the disease but will need to follow further.

Over 100 other dogs of 11 different breeds have not had this mutation.

In study 3 dogs were negative and had VPCs, but were older dogs and they could point to other causes (tumors, etc.) for the arrhythmias.

New drug for heart failure (not ARVC); vetmedin or pimobenden.

Welcome to send questions - a little buried so may take some time for a response (a week or so).

Gold standard is staining of heart muscle to determine strength of cell connection; difficult to do because need immediately-frozen heart. This is not an association test - deletion is either there or not - clearly not in unaffected dogs and clearly not in other breeds, but not enough hearts to give statistics.

CoQ10 - only shown to be useful in humans with certain disease, has not been shown to be useful in dogs (won't hurt but probably not worth expense).

Searching for mutations of other associated genes would be step 2. Don't know about continuing study - time, energy, will to go on!, funding.

Sotalol is not generally pro-arrhythmic, extremely safe in dogs, but it is always possible that it could increase arrhythmias. Recommend repeating holter in 2-3 weeks after starting; very very rare but dog could get worse with Sotalol. More likely that it just did not help; some dogs need sotalol plus mexilitine - repeat holter may look higher, not that dog is worse just variability.

Outreach information for GP vets - presented to veterinary cardiologists at cardiology conference last week. This type of outreach (presentation) hasn't caught on as much with general public and vets as it has with breeders.