Disclaimer: These are from my notes and recollections and any mistakes contained are mine, not the speaker’s.
The study vets are Dr. Stepien and Dr. Kellihan. The Whippet Cardiac Health Project started in 2004 and gathered data until 2015. Some of the questions they were looking to answer are:
What is the prevalence of murmurs?
What’s causing these murmurs?
Can an auscult screen identify heart disease?
How many murmurs are due to valve disease and how many are athletic?
Heart Murmurs – 3 types
Functional (innocent, athletic, ejection)
- No anatomic abnomalities
- No function abnormalities
Mitral Regurgitation due to valve disease
- myxomatous mitral valve disease (MMVD)
Mitral regurgitation due to heart enlargement
- dilated cardiomyopathy
The grade of a heart murmur related to the intensity of the sound. There is a point of maximal intensity (usually the left). Mitral murmurs are usually loudest at the apex of the heart, whereas athletic murmurs are more towards the base.
The intensity of a murmur is related to the severity of the disease.
Soft 1-2
Moderate 3-4
Loud 5-6
The normal heart beat makes a sound like “LUB DUP”. The murmur is a whooshing noise between those 2 sounds, making them less distinct.
There was a study in the EU that included 105 healthy whippets.
- 42% had no murmur
- 58% had some murmur
In another study involving 200 healthy US whippets:
- 93% had a murmur
- 7% had no murmur
When the cause was discerned via auscultation:
- 64% were diagnosed as atheltic
- 29% were diagnosed with mitral regurgitation
- still had the 7% with no murmur
When actually looked at via echo it was found that of those 93%
- 38% had mitral regurgitation (vs. 31% on auscult)
- 62% were athletic (vs. 68% on auscult)
Mitral regurgitation can be missed on auscultation alone!
The worst grade for correct identification is grade 2, less than 20% are correctly identified. The louder and softer murmurs are easier to discern.
Normal heart valves are thin and clear. Disease causes thickening, lumpiness and bumpy edges, all of which interfere with the valves correct seal. This causes leakage. In mitral valve disease you can see the valves flapping all over and at later stages can cause a hyper contractile heart as it works harder to overcome the leakage.
Mitral valve prolapse can cause eccentric jets (an eccentric jet is a backflow of blood through the valve that is not centrally located) which are indicative of disease. The degree of prolapse is related to the degree of leakage. Often you will also see ruptured chords, which are tiny tendons that help anchor the valve flaps within the heart. They look like small threads on the valve, and add to the floppiness of the valve.
Staging Mitral Valve Disease
Normal –> MVD –> Heart Enlargement –> Symptoms
Prevalence of MVD by age (any degree)
- 22% of 4-5 year old
- over 50% of 6-7 year olds
- over 75% of 9-10 year olds
What does an enlarged heart mean?
First ask your cardiologist if the heart was compared to breed normal, not just canine normal. Whippets tend to have larger hearts than most breeds. All heart diseases lead to enlarged hearts. An enlarged heart does not equal dilated cardiomyopathy.
Biomarkers can be used to help diagnose heart disease.
- NT-Pro BNP – an indicator of cardiac stress
- cTnI – indication of cardiac tissue changes
Both will be higher in the presence of mitral valve disease.
Genetic Markers
Dr. Stern is working on a test to identify genetic markers for earlier onset MVD in whippets. It appears to be heritable with a unique genetic signature, located on chromosome 15 in whippets. Hopefully in the future we will have a DNA test available to us.
In dilated cardiomyopathy every chamber of the heart will be enlarged, plus there will be reduced contractile function. This has a low incidence in whippet but is a high impact disease for the individual. There is primary DCM and secondary, secondary can be causes by hypothyroidism or low blood taurine. Currently they are collecting DCM cases for genetics, if you have a dog affected please contact Dr. Stepien.
In DCM the heart is not contracting as well. Diagnosis should be done via live exam. Do not trust a DCM diagnosis via necropsy because many of the signs are related to how the heart beats, and a deceased DCM heart may appear very similar to a deceased MVD heart.
Taurine
If you suspect low taurine as a cause be sure to test whole blood taurine levels, not plasma. Dogs can synthesize taurine if they have precursors in their diet. Their diet or gut bacteria may interfere with this process.
Diets that have been linked to low taurine levels:
– lamb and rice
– raw
– legumes (peas, lentils etc)
In whippets with DCM 27% have lower than normal taurine levels. None of the whippets tested were above 250 nmol/mL.
Whippets are like other dogs with mitral valve regurgitation, in that the prevalence in the population increases with age, and the regurgitation itself is progressive and gets worse with age.
Whippets are different than other dog breeds in that many dogs live with severe disease with no clinical signs. Many of these dogs are top athletic competitors.
Questions to ask to assess valvular disease
– How big is the mitral regurgitation jet?
– Is the jet central or eccentric?
– Is there visible mitral valve prolapse?
Questions to ask upon a diagnosis of dilated cardiomyopathy
– Were the measurement compared to breed normal?
– Were whole blood taurine levels assessed?
Breeding programs should focus on delaying the onset of MVD in whippets. Staging of MVD is possible in whippets. Biomarkers and genetic tests may be available in the future.
Recommended Taurine dose for a whippet with low blood taurine:
500mg 2x a day, use GNC tablets (not capsules)
What are symptoms of MVD?
– cough
– exercise intolrance
– fluid in lungs and abdomen
Many whippets can have severe MVD with no signs or symptoms.