The following information on Subaortic stenosis (SAS) in German Boxers was reported recently in the Boxer Blaetter, the official publication of the Boxer Klub of Germany.
The Boxer seems to have a higher incidence of subaortic stenosis than many other breeds. In the most severe cases, collapse and sudden death can occur.
This problem is already known in the Boxer population of England, France and Norway, and of course, our own United States.
The German Boxer Klub did extensive testing on 89 Boxers that were chosen at random. It was first determined if the dogs had heart murmurs, since these are generally present in dogs with SAS. (However, not all dogs with heart murmurs actually have SAS; this must be determined by echocardigram with color Doppler.)
Internationally, a value of 2 m/s is accepted as the limit uppermost limit. (OFA limits are 1.7 with higher than 1.7 up to 2.0 considered a "gray" area.) Animals with higher values are to be considered affected with aortic stenosis.
The German evaluations led to some disturbing findings. About half of all examined animals displayed a heart murmur, which was classified as a heart murmur of class 2 or higher. Heart murmurs are divided on a scale of 0 to 6. Heavy noises of classes 5 and 6 did not occur in any of the 89 dogs. Only about a third of the animals were classified into class 0. The median value of the velocity for the entire random sample laid within 1.85 + / -0.6 m/s. 47% of the dogs had velocities of 2 m/s or more. The average velocity in the individual age groups (one to six year old Boxers were represented) does not differ statistically. That is to say, that in animals over a year of age, there was no tendency for SAS to progressively develop.
At the present time, the German BK has not made any determination concerning SAS and animals to be used for breeding. Since many of our members have dogs of German origin, we will be keeping a close watch to see what recommendations will be made by the BK.
The following information is reprinted with permission from the Clinical Cardiology Concepts homepage and was written by Dr. Michael R. O'Grady, DVM, MSc, Diplomate ACVIM (Cardiology), Staff Cardiologist at Veterinary Teaching Hospital, University of Guelph.
For more information on SAS, and other heart problems
in animals, check out their excellent homepage at CLINICAL CARDIOLOGY CONCEPTS - Contents
Aortic Stenosis
What is the abnormality?
Aortic stenosis is reported to be the third most prevalent congenital cardiac disorder in the dog. Our present work suggests that aortic stenosis is by far the most common congenital cardiac defect in the dog. The stenotic lesion may occur in the subvalvular position, valvular position, or supravalvular position. The subvalvular disorder is the most common in dogs.
The hemodynamic consequences of aortic stenosis is the development of left ventricular concentric hypertrophy. This results in reduced left ventricular distensibility and the hypertrophied left ventricular wall is prone to initiating dysrhythmias.
What is the prognosis with aortic stenosis?
•Most cases of aortic stenosis of marked severity result in malignant dysrhythmias and sudden death.
•Mild cases of aortic stenosis live a full life (both normal quality and duration).
•Even cases of moderate stenosis can anticipate a life of normal length and quality.
•Work with Doppler echocardiography has revealed that if the velocity of flow across the left ventricular outflow is less than 4 m/s by the time the dog is mature, it appears that the dog can anticipate a life of normal length and quality. If the velocity of blood flow is greater than 5 m/s by the time the dog is mature, it will likely succumb to this disorder.
•Work with Doppler echocardiography indicates that aortic stenosis is a progressive and that the rate of progression is greatest in the immature dog and progresses at a very slow rate in the mature dog.
•It has been reported that if dogs survive with aortic stenosis beyond 3 years, they usually do not have aortic stenosis severe enough to produce a marked effect on LV performance.
How does aortic stenosis present?
1. Signalment:
•Breeds: Newfoundland, German Shepherd, Boxer, Golden Retriever, Bull Terrier, Bouvier de Flanders, Bernese Mtn. Dog, Rottweiler
•Age: Presented as puppies at the time of the first vaccination - an incidental finding. May present as adults with an incidental murmur
2. History:
Presented for vaccination, the heart murmur is an incidental finding. Usually asymptomatic. Syncope (fainting), sudden death may occur.
3. Physical examination:
Systolic heart murmur with a PMI over the left heart base radiating up the neck, and to the right hemothorax. The femoral arterial pulse may be weak. Signs of heart failure are rare. Dysrhythmias with pulse deficits may be noted. At times the PMI for this disorder is over the right heart base.
How is aortic stenosis diagnosed?
The definitive diagnostic tests for aortic stenosis:
a.Doppler echocardiography (non-invasive)
b.Cardiac catheterization (invasive)
A presumptive diagnosis can be made with: ausculation of a left basilar systolic heart murmur, weak femoral arterial pulse, left ventricular enlargement on EKG, left ventricular enlargement on radiography.
Diagnostic Findings:
a. Radiology may see: left ventricular enlargement, dilation of the aortic arch particularly on the lateral view in the region of the "right auricle/main pulmonary artery /ascending aorta", frequently radiographs are normal.
b. EKG: usually normal, may see criteria of left ventricular enlargement, may see ventricular ectopy (PVC's).
c. Echocardiography: left ventricular hypertrophy (concentric), subvalvular lesion, increased velocity across the aortic valve by Doppler, aortic regurgitation by Doppler in about 85% of cases.
How is aortic stenosis treated?
(Generally, mild cases are not treated. Treatments below are for more severe cases).
1. Correct dysrhythmia: beta blocker therapy or Class I antidysrhythmic therapy.
2. Improve left ventricle distensibility: beta blocker therapy.
3. Surgical correction: presently not feasible, a number of procedures are being evaluated.
4. Heart Failure is very rare: Is more likely to occur in cases of moderate and severe aortic stenosis if concurrent mitral valve insufficiency is present and severe.
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