As some of you know from past Boykin Spaniel Society newsletters, Pulmonic Stenosis is a growing concern with our breed. This article is not here to alarm anyone, simply to inform. An article I wrote for the newsletter, "An Expensive Discovery" was written almost two years ago. The response from the membership has been very small. I know I am not the only owner/breeder with this health issue.
This is not going to go away by pretending it doesn't exist. One of my client dogs (no relation to my line) was an 11-month old, beautiful, retrieving machine. She died of massive heart failure in the dove field last fall. I recently whelped a litter of eight pups and one female has a severe case of pulmonic stenosis and will not live to see her second birthday. Both parents are OFA cardiologist certified as are all of the grandparents. Since it was one in eight it may be a fluke of nature and not an indicator of things to come. To be safe, the dam will be spayed and the sire closely monitored in any future breeding.
Right now there is no way of knowing if your dog is a carrier of heart disease. When there is a heart study conducted where the DNA can be examined in hundreds of dogs and the genes responsible pinpointed, then we can see the markers and not breed now-unknown carriers.
To this end I am starting to collect the DNA on families of my Boykins for storage. It may be next year, it may be five years from now before the problem gets serious enough to warrant funding for the research. I am collecting samples and sending them in to VetGen - Veterinary Genetic Services to be stored for up to ten years.
I am starting with this new pup. I will collect DNA from her, two of her unaffected siblings and her parents. If there was another affected puppy then a sample from that pup would be needed as well. So, six samples at $35.00 each, for a total of $210.00 per family. Next I will get kits for the older litter that had three pups with pulmonic stenosis - get samples from 2 of the affected pups, 2 unaffected, and the parents. If anyone out there has a living dog (no matter what breed) with pulmonic stenosis or some other congenital heart disease, please contact VetGen and start saving that DNA.
The following information is from the Canine Inherited Disease Database
What is pulmonic stenosis?
As part of normal circulation in the body, the right side of the heart (the right ventricle) pumps blood to the lungs to receive oxygen. The oxygenated blood goes back to the left side of the heart from which it is pumped out to the rest of the body.
Blood flows from the right ventricle of the heart through the pulmonic valve into the pulmonary artery and thence to the lungs. With pulmonic stenosis, there is partial obstruction of normal blood flow, most commonly due to a malformation of the pulmonic valve ("pulmonic valve dysplasia") but the abnormality may be immediately above or below the valve as well.
The effect of this partial obstruction is to force the heart to work harder to pump blood to the lungs. The extent to which a dog will be affected depends on the degree of narrowing (stenosis) of the valve area. With severe stenosis the dog will likely develop congestive heart failure due to the increased workload of the heart.
How is pulmonic stenosis inherited?
Pulmonic stenosis appears to be a polygenic threshold trait. Polygenic traits are controlled by an unknown number of genes. The gene expression is influenced by a variety of factors including gender, nutrition, breed, rate of growth, and amount of exercise. These traits are quantitative traits - that is, there is a wide range within the population. Such traits include height, weight, character, working abilities, and some genetic defects. Heritability varies within different breeds and within different populations of a particular breed.
Because it is virtually impossible to determine the exact genotype for such traits, it is difficult to control defects with a polygenic mode of inheritance. The best attempts at control are based on a grading scheme for identification of the defect and a breed policy of recording and publishing the results for as many dogs as possible.
What breeds are affected by pulmonic stenosis?
Pulmonic stenosis is one of the most common congenital heart defects in all species. There is a breed predisposition in the following breeds of dog:
The English bulldog and the mastiff are at most risk for pulmonic stenosis. In English bulldogs, pulmonic stenosis occurs commonly with an abnormal left main coronary artery branch, arising from a single right coronary artery. In this breed the condition is more common in males.
There is also an increased risk of pulmonic stenosis in the beagle, wire-haired fox terrier, chihuahua, miniature Schnauzer, samoyed, Boykin spaniel, West Highland white terrier, cocker spaniel, Airedale terrier, and Scottish terrier.
For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a general consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed.
What does pulmonic stenosis mean to your dog & you?
In its milder forms, the slight thickening of the pulmonary valve will cause minimal or no obstruction and your dog will not be affected. However with more severe thickening of the valve, the obstruction to blood flow from the right side of the heart will cause varying degrees of heart damage which worsens with age. With moderate-to-severe pulmonic stenosis, your dog may experience signs associated with low cardiac output and/or right-sided heart failure, such as respiratory difficulties, fainting, tiring with exercise, abnormal cardiac rhythms, abdominal swelling due to an enlarged liver or the accumulation of fluid because of failing circulation, or sudden death.
Based on your dog's physical examination and diagnostic tests such as chest x-rays and an electrocardiogram, your veterinarian will discuss with you the severity of the pulmonic stenosis. If there are significant changes evident, he or she will suggest further tests to determine the pressure gradient across the pulmonic valve. (Normally there is no pressure difference between the right ventricle of the heart, and the pulmonary artery to the lungs.) Where there is a pronounced pressure gradient, surgery to correct the stenosis should be considered.
How is pulmonic stenosis diagnosed?
The first indication that your dog has a problem may be when your veterinarian hears a heart murmur on an early physical examination. Alternately, you may see signs in your dog related to heart disease, such as fainting or fatigue with exercise. Your veterinarian will listen carefully to try to determine the location of the murmur and to differentiate it from an "innocent" murmur which disappears by about 6 months of age. If the murmur is significant, your veterinarian will suggest further tests such as a chest x-ray, electrocardiogram, and cardiac ultrasound to help determine the cause, and to see what changes if any have already occurred in the heart as a result of the defect. Once pulmonic stenosis has been diagnosed, Doppler echocardiography or cardiac catheterization can be done to measure the pressure gradient between the right ventricle and the pulmonary artery, to determine the severity of the obstruction. Based on these test results your veterinarian will discuss with you the long term prognosis for your dog and whether surgical correction of the defect should be considered.
FOR THE VETERINARIAN:
1. MURMUR: systolic ejection murmur, loudest in pulmonic area near left cranial sternal border, often equally loud along right cranial sternal border.
2. ELECTROCARDIOGRAM: RV hypertrophy and right axis shift, right atrial enlargement, possibly arrhythmia associated with hypertrophy.
3. RADIOGRAPHS: right ventricular hypertrophy , poststenotic dilation of pulmonary artery with distal pulmonary vessels reduced in size.
4. ECHOCARDIOGRAPHY: primary means of diagnosis of pulmonic stenosis, typically see mild to moderate right atrial dilation, concentric RV hypertrophy, deformity and narrowing in the pulmonic valve region, and poststenotic dilation of the pulmonary artery.
5. jugular pulses may be evident.
In English bulldogs, pulmonic stenosis is commonly associated with a left coronary artery anomaly which has important implications for surgical correction.
How is pulmonic stenosis treated?
With mild-to-moderate stenosis, your veterinarian will monitor your dog. No other treatment is necessary unless clinical signs develop which are associated with heart disease. Surgery is an option in dogs with moderate-to-severe pulmonic stenosis, with different techniques recommended depending on the site of the stenosis. Because of the expertise and technical equipment required and the surgical risk involved, surgery to correct pulmonic stenosis is generally performed in a referral centre.
Surgery is more risky if atrial fibrillation or congestive heart failure have developed. These conditions should be treated medically and the dog stabilized before surgery is considered.
Medical management for congestive heart failure is similar no matter what the cause, and consists of medications to support the heart muscle and decrease the work load of the heart, together with dietary recommendations.
According to the VetMedCenter:
How is pulmonic stenosis treated?
A procedure called "Balloon Valvuloplasty" can be used to relieve the obstructed valve. During this procedure, a catheter is passed into the heart while the animal is under general anesthesia. A balloon is inflated to dilate the narrowed valve. The results can be very good, though final results can depend on the type of narrowing present. With some forms of pulmonic stenosis, balloon valvuloplasty may not result in much improvement. In these cases, surgery may be recommended to enlarge the obstructed valve. If heart failure has developed, fluid will accumulate in the abdomen and diuretic drugs may be given to help clear the excess fluid.
What is the prognosis for animals with pulmonic stenosis?
The prognosis is excellent for animals with mild pulmonic stenosis. For animals with severe pulmonic stenosis, the prognosis is guarded. Without some form of treatment to relieve the obstruction, most of the severely affected animals are at risk of heart failure, or premature death. Balloon valvuloplasty is a comparatively safe procedure. The risks associated with other surgical procedures are somewhat higher, and surgery is generally only carried out in the most severe cases.
Affected individuals and their parents should not be used for breeding. Siblings should only be used after careful screening. If any affected offspring are born, breeding of the parents should be discontinued.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Other informative links:
To read more about inherited heart diseases you can go to the
OFA web sight: OFA
University of Pennsylvania
VetGen Veterinary Genetic Services