Health - Hearts



 

Heart conditions are on the rise within the French Bulldog due to irresponsible breeders;
the below article outlines some of the more common heart conditions that can occur
 

Cardiomyopathy
 Cardiomyopathy may be congenital (present from birth) or develop when the dog is elderly. It is a disease of the heart muscle. Simply put, the heart muscle enlarges and weakens. This makes it inefficient in pumping blood through the body. Whilst diseases, like parvovirus, may play a role, the condition is usually hereditary and present from birth (congenital). As the enlarged heart becomes less and less efficient, fluid begins to build up - in the lungs and abdominal area in particular. This causes the characteristic early morning and night-time coughing. Coughing may often be accompanied by greyish or blueish gums, panting, and a reduced appetite which results in a very thin dog. A potbelly may appear as a result of the retained fluids in the abdominal area. Eventually, the dog has a bloated or obese appearance from the water retention
associated with a failing heart.
Dogs with heart problems tend to try to sleep sitting up. They commonly assume a sitting position with the front legs spread apart and the head extended to try take in more air.
Fainting spells may occur, which are often mistaken for fits or epilepsy
.
 
Symptoms of heart disease:
*           Shortness of breath
*           Reduced exercise tolerance
*           Difficulty breathing
*           Coughing
*           Noticeable weight gain or loss
*           Swollen abdomen
*           Fainting
*           Loss of appetite
*           Depression
*           Nasal discharge
 
Consult with your Vet should two or more symptoms be present.
 
Accurate diagnoses are possible by using x-rays or ultrasound, where the presence of cardiomyopathy in the pedigree is unknown. Drugs to help the heart are available and may prolong life. They are usually administered at the same time as drugs that treat water retention.
 
Low salt diets are recommended and your Vet may suggest that you switch from
your regular brand of dogfood. This is because salt increases fluid retention,
already a problem when the heart is not working properly.
 
Your dog should not be allowed to be overweight when he presents with cardiomyopathy – although most dogs with hereditary cardiomyopathy tend to be skinny.
Older dogs with age-related heart disease
tend to be overweight,
which requires management by the dog’s owner.
 
Exercise needs to be monitored, as your dog needs to be fit, but not to over-exert himself.
 
Cardiomyopathy is occasionally associated with other conditions or disorders, like hypothyroidism. Diseases like parvovirus may sometimes weaken the heart, creating conditions suitable
for heart disease to
develop. Heartworm, is now also of concern.
 
Dilated cardiomyopathy is one of the most common heart diseases in adult dogs. Large breeds are most commonly affected, with three-quarters of the affected dogs being male. Affected females have a markedly lower survival rate than affected males. Survival statistics are poor.
 
Heart Murmurs
 
A murmur can usually be heard when the puppy is 10 weeks old – although it can be picked up earlier by a very experienced Vet, this is very difficult as the puppy has a very fast heart rate, fidgets and sniffs. It is
not easy for a Vet to determine the difference between a puppy murmur and a congenital heart
defect murmur by listening with a stethoscope (auscultation).
 
Murmurs are generally caused when;
*        the valves of the heart, operating as one-way valves, “leaks”. The blood thus flows forwards AND squirts backwards with every heartbeat. This creates the characteristic sound of a heart murmur,
*        a valve is abnormally narrowed, pinching the blood flow
*        a hole in the heart produces a murmur when blood is squirted through the hole,
*        puppies under 6 months of age may have puppy murmurs, which they gradually grow out of,
*        when a dog is anaemic, and has “thin” blood. The thinner blood flows faster through the heart causing a consequent murmur,
*        when a dog has a fever, or is receiving medications known to “thin” the blood.
 
ECGs and X-rays may be needed to definitively diagnose a heart murmur, and to determine what type of murmur it may be.
 
SAS
(subvalvular aortic stenosis)
 
Subaortic stenosis is the second most common canine heart malformation. It is defined as an "obstruction of the left ventricular outflow tract that ranges in severity from an incomplete fibrous ridge to a fibromuscular tunnel", and lies just under the aortic valve. This lesion causes turbulence in the blood as it crosses the aortic valve, and creates a murmur in most affected dogs. The lesion develops postnatally, unlike other congenital / hereditary heart diseases. "Congenital" is somewhat of a misnomer in the case of SAS. The subaortic lesion progresses with maturity. Heart murmurs can be detected as early as six to eight
weeks of age, or develop as late as three to four years of age in milder cases.

Most of the information available on SAS, including inheritance of the defect, has come from breeding studies done on Newfoundland dogs. Information from this breed is identical to the clinical features observed in other SAS affected breeds, such as Rottweilers and Golden Retrievers. The mode of transmission found in the Newfoundland dog breeding studies suggests an autosomal dominant gene trait with variable expression or penetrance is responsible, with the variability probably due to modifying gene factors. This makes the true mode of inheritance complicated, presenting a challenging problem in removing the defect from the dog population.

Regardless of the degree of severity observed, any affected SAS animal can produce a degree of severity in its offspring because of the dominant genetics of the disease.

Subaortic stenosis has been graded  based on post-mortem exam:
*        Grade 1 is the mildest form, with raised white nodules occurring in the area under the aortic valve;
*        Grade 2 is the intermediate form, with a fibrous ridge that partially encircles the outflow tract;
*        Grade 3 is the most severe form, with a fibrous band encircling the entire outflow tract just under the aortic valve, and may also cause changes in the mitral valve complex.
 
The mildest lesions create the most frustrating problem for breeders. While 95% of all cardiac defects cause a heart murmur, the Grade 1 lesion of SAS does not always create enough change in blood flow to cause a clinically detectable heart murmur. In studies performed on Newfoundlands, it was found that ausculation (stethosope exam), cardiac catheterization, and echocardiography (ultrasound), the most technologically advanced methods to detect and define heart murmurs, failed to reliably detect some, if not most, of the mildly affected dogs, as determined by post-mortem exam.
 
The Grade 2 lesions are often associated with soft cardiac murmurs and minimal changes in the pressure gradient across the aortic valve.
 
The Grade 3 lesions are usually associated with the more severe clinical signs, including moderate to severe murmurs, exercise intolerance, syncope (fainting), congestive heart failure, and sudden death.
 
The importance of this clinical data is clear - while the genetic makeup for SAS may be present in a dog, the actual detection of subaortic stenosis becomes difficult in mild cases, with definitive diagnosis
of the carrier depending on post-mortem exams. This makes genetic counselling for this genetic
trait difficult and leaves breeders frustrated.

Treatment for SAS can be frustrating.
Mild Cases:Therapy is usually not indicated in mild cases, as affected dogs are usually asymptomatic and can live a full and productive life.
The only exception requires the use of prophylactic antibiotics for potential bacterial problems; such as dental procedures, surgery, and wounds; due to the risk of the dog developing endocarditis (bacterial colonization of the heart valves), which may damage the heart valves.
 
Moderate to severe cases: For moderate to severe cases, treatment is limited to drugs aimed at decreasing the clinical symptoms, such as those associated with congestive heart failure. However, the benefits of such drug-oriented treatment are minimal. Many moderate to severely affected dogs may develop acute heart arrhythmias as a result of heart muscle ischemia and sudden death. It is thus perhaps better to use a holistic approach based on nutrition, moderate exercise, a wellness-oriented lifestyle and dollops of affection.

How can breeders decrease the incidence of subaortic stenosis?
Firstly, the limitations of current diagnostics in recognizing mildly affected dogs must be recognised. It is also known that many affected animals shall be identified in a comprehensive program of screening. A carefully planned program of screening - and definitively diagnosing heart murmurs, along with genetic counseling - could reduce the incidence of the defect within a few generations. This includes screening all breeding stock, then carefully screening all progeny for the defect and eliminating parents which have produced affected offspring.

A Conservative Program to Screen Dogs for Discrete Subaortic Stenosis (see reference1)
*        Most, but not all, discrete subaortic lesions will produce a murmur, and it is reasonable to use ausculation (stethoscope examination) as the main screening method. Some very mildly affected defects will go undetected, but neither are these likely to be detected by ultrasound or catheterization.
 
*        Because the lesion develops postnatally, screening should not be begun until 6-8 weeks of age. Pups with murmurs should be examined by more definitive methods, as needed, to make a diagnosis. Moderate to severe subaortic stenosis can be diagnosed by this age. Pups with mild lesions may not be distinguishable from those with innocent flow murmurs.
 
*        Pups with low grade murmurs and no other evidence of heart disease should be re-examined at 12-14 weeks of age. If the murmur disappears, the pup can be considered clear of clinically significant congenital heart disease. However, if there are close relatives with subaortic stenosis, it is prudent not to use such animals for breeding stock or use them only if their offspring are carefully screened for congenital heart disease. Discontinue breeding such dogs if they produce pups with confirmed subaortic stenosis.
 
*        Pups with a low grade murmur that persists beyond 12 weeks should be re-examined by more definitive methods to make an accurate diagnosis. If echocardiography (ultrasound) or cardiac catheterization and angiocardiography are used, it should be possible to reduce the number of false positives. Pups that have a persistent murmur consistent with subaortic stenosis, but have no evidence of a congenital heart defect after further studies can be considered clear of a clinically significant lesion, but a very mild lesion cannot be ruled out. Such animals should not be used for breeding unless there are other compelling reasons for it. If bred, the offspring of such dogs should be carefully screened for evidence of
congenital heart disease and breeding discontinued if any affected pups are produced.
 


References:


1. Genes and the Heart: Congenital Heart Disease. Donald F. Patterson DVM, DSc, Diplomate ACVIM; 1991 Academy of Veterinary Cardiology Proceedings, as presented in conjunction with the 58th Annual Meeting of the AAHA and the Ontario Veterianary Medical Association Meeting, April 13-14, 1991, Toronto, Ontario, Canada.

2. The Genetics and Pathology of Discrete Subaortic Stenosis in the Newfoundland Dog. R.L. Pyle VMD, MS, D.F. Patterson DVM, DSc, S. Chacko DVM, PhD, American Heart Journal, Vol. 92, No. 3, pp. 324-334, September 1976.

3. CVT Update: Canine Subvalvular Aortic Stenosis. Linda B. Lehmkuhl and John B. Bonagura, Kirk's Current Veterinary Therapy, Volume XII, 1994.

4. OFA Congenital Heart Disease Registry: General Procedures. Orthopedic Foundation for Animals, 1996.

 


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