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You could’ve heard a pin drop: for the first time since the big brouhaha in the late 90’s that resulted when cardiologist/researcher Dr Kate Meurs suggested that more-than-50 VPC’s might be the difference between "normal" and "affected" (with Boxer Cardiomyopathy), she gave her audience of avid boxer breeders/exhibitors at the ’05 ABC Membership Meeting some more-or-less firm parameters – numbers of VPC’s for BCM (ARVC); flow rates for SAS – by which to assess the heart-health of our breeding stock and make breeding decisions.

Yes, individual judgment and common sense are still required: the guidelines for BCM are fairly broad, and Dr Meurs continues to stress that we should NOT make significant breeding decisions based on a single Holter test.

But the guidelines for SAS, although far more liberal than they used to be, don’t leave a lot of room for interpretation.

Let’s start with BCM, or ARVC:

Dr Meurs gave a brief history of the disease in boxers, and explained that she had renamed it "Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)," to more accurately describe it as an electrical disease, as opposed to the kind of cardiomyopathy (heart muscle disease, or dilated CM) that most often affects Dobermans and Danes.

Dr Meurs noted that ARVC is an adult onset disease, which affects the dog at variable ages – 3/4, 5/6/7. She said a heart murmur was NOT typical of ARVC; instead diagnosis consists of the identification of VPC’s (Ventricular Premature Contractions) on a Holter monitor tape (24-hour EKG). Dr Meurs stressed that the Holter tape should be read and interpreted by a board-certified cardiologist, because a computer reading often misinterprets artifacts as VPC’s.

Dr Meurs also said that it was NOT common for a normal dog to have more than 100 VPC’s in 24 hours, or to have couplets, triplets, or runs. Normal large-breed dogs have an average of 2 VPC’s per day. Therefore, she considered the ARVC status of a boxer that had 100 VPC’s to be "indeterminate"; 100 – 500 to be "suspicious"; and more than 500 to be "affected." Genetically, Dr M. believes ARVC is the result of an autosomal (not sex-linked) dominant gene with variable penetrance.

She added that it’s ok to Holter a bitch in season; but is NOT ok to echo a bitch in season, as the results may be skewed.

AS/SAS:

Sub-aortic Stenosis is a congenital heart defect – a fibrous ridge below the aortic valve. It is a familial disease, and most of the information we have is based on Newfie studies.

However, Dr. Meurs has conducted a new study of SAS, in which 201 boxers were evaluated: 56% of them had at least a soft murmur, and the median maximum velocity of blood flow across the aortic valve was 1.9 m/s. Only 9 boxers had a flow rate of less than 1.5 m/s. Most of the murmurs occurred in young dogs. There were fewer murmurs in older dogs due to less excitement in the older dogs during the test.

Valvular dimensions: in her studies of boxers and non-boxer dogs, Dr Meurs found that non-boxers had significantly larger indexed valvular areas – i.e. aortas. As a result of her recent studies, Dr M suggested the following flow-rate guidelines:

Less than 1.7 – 2.25 m/s = normal (in the absence of any sign of a fibrous ridge or turbulence).

2.25 – 3.0 m/s = mildly affected.

3.0 – 4.0 m/s = moderately affected.

More than 4.5 m/s = severely affected.

Dr Meurs cautioned against the vigorous removal from a breeding program of dogs with borderline values or murmurs. She also said that if a board-certified cardiologist does not hear a murmur with a stethoscope, it is NOT necessary to do a Doppler exam.

Dr Meurs’ report ended on a very happy note, with the news that she and her staff had done 104 echoes at the ’05 ABC, and had thereby raised $10,000 for her ongoing ABCF heart study!