For The Health of Your Mini...

A new column dedicated to addressing the health concerns of the MBTCA membership.

If you have an article that you feel might be pertinent to this column, please submit it to the editor before the ad deadline for the issue in which you would like it to appear

Update on Miniature Bull Terrier Left Heart Abnormalities

The following report was submitted by B.K. Lefbom, DVM, DACVIM (Cardiology) & S.L. Rosenthal, DVM, DACVIM (Cardiology) Chesapeake Veterinary Cardiology Associates, Springfield, VA, Annapolis & Timonium, MD, M.B. Lesser, DVM, DACVIM (Cardiology) Advanced Veterinary Care Center, Lawndale, CA.

Over the past few years, independent cardiology groups have been noticing abnormalities in the Miniature Bull Terrier (MBT) breed. We are currently consolidating our data to obtain relevant numbers of dogs and generate the most meaningful data possible. As we discussed at the meeting in San Diego, several noticeable abnormalities are present when we screen MBT's echocardiographically.

The most prominent abnormality is a consistent increase in the velocity of blood flow through the left ventricular outflow tract (blood flow from the left ventricle out to the body). Accepted normal values in other breeds generally range from 1 to 1.5 m/sec. Equivocal velocities are from 1.7 to 2.2 m/sec. Based on the data thus far collected, over half (54%) of all MBT's screened fall into the equivocal range and almost all of the remaining dogs (41%) are distinctly abnormal. Some basic math reveals only 5 % of all MBT's screened thus far have normal LV outflow velocities.

Concern has arisen because multiple operators have screened some dogs and alternate numbers are generated. Based on the Doppler principles in place for velocity analysis, the only way to err is on the low side. There is virtually no way a cardiologist can generate a falsely high number. The most accurate measurement of the outflow area is obtained via the subcostal view. This view requires the transducer to be placed on the abdomen and images the heart deep to the liver. If this technique is not used, the alignment of the ultrasound beam may be less than ideal and a lower number will be generated. Review of our data consistently shows a higher velocity is obtained when the subcostal approach is taken.

Another potential cardiac concern in Miniature Bull Terriers is the conformation of the mitral valve apparatus. A significant percentage of dogs (92% in one screened group) have shortened mitral valve chordae and/or a small amount of mitral regurgitation. Also, many affected dogs do not have audible murmurs. Therefore complete echocardiographic examination is required to evaluate for these potential problems.

None of the dogs screened thus far have been symptomatic cardiac disease nor are they expected to develop congestive heart failure. A single dog has experienced sudden death although we do not have confirmation of the exact cause at this time. The overwhelming concern for the breed is that propagation and intensification of minor abnormalities can be predicted to occur.

Thus, continued matings of minimally affected dogs could produce moderate to severely affected offspring. The conclusions made so far suggest that breeding animals should be screened aggressively prior to their use. If breeding animals are found to have multiple mild defects or LVOT velocities > 2.2 m/sec, they should be considered at risk for producing more significantly affected offspring. In these situations it is the responsibility of the breeder to make the appropriate breeding decision.