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Common names or abbreviations:
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Pulmonic stenosis
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Pulmonic stenosis with anomalous
left coronary artery
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Type A pulmonic stenosis
(pulmonary ostium hypoplasia)
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Valvular pulmonic stenosis
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Description or definition:
| Pulmonic stenosis is a congenital narrowing in the
region of the pulmonary valve, which lies between the right ventricular
chamber of the heart and the pulmonary artery. As part of the normal
circulation 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. |
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 dogs will
likely develop congestive heart failure due to the increased workload of the
heart. The hemodynamic consequences of pulmonic stenosis are the development
of right ventricular concentric hypertrophy (enlargement) and reduced filling
of the left ventricle. The right ventricular concentric hypertrophy causes
reduced right ventricular compliance with reduced distensibility. The
hypertrophied right ventricular wall is prone to initiate dysrhythmias.
Pulmonic
stenosis can occur with other defects and it is one of the components of
another congenital defect: Tetralogy of Fallot.
| The stenotic lesion may occur in the:
| Subvalvular position – below the valve at the
conus arteriosus or infundibulum. |
| Valvular position – within the valve itself
(commonest site). |
| Supravalvular position – above the valve in the
pulmonary artery itself (rare)
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| Usually, affected animals show no external signs of
the disease and it is frequently diagnosed during routine examination of
the heart with a stethoscope (auscultation). 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, if blood flow is
seriously impaired, signs associated with right –sided heart failure may
be seen including poor exercise tolerance, respiratory difficulties,
abdominal swelling due to an enlarged liver, feinting (syncope), or sudden
death.
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| 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.
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| Pulmonic stenosis is reported to be the 2nd
most prevalent congenital cardiac disorder in the dog. Aortic
stenosis being the most common congenital heart disorder.
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| There is a breed predisposition in the following
breeds of dog: |
English
Bulldog, Mastiff, Beagle, Wire-Haired Fox Terrier, Chihuahua, Miniature
Schnauzer, Samoyed, Boykin Spaniel, West Highland White Terrier, Boxer, Cocker
Spaniel, Airedale Terrier and Scottish Terrier.
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Diagnosis can be broken
down into two areas:
| Presumptive diagnosis:
| Auscultation of a left basilar systolic
heart murmur. |
| Normal femoral arterial pulse |
| Right ventricular enlargement on EKG |
| Right ventricular enlargement on
radiography
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| Definitive diagnosis:
| Doppler echocardiography |
| Cardiac catheterization
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| Diagnostic findings:
| Radiology may show:
| Right ventricular enlargement |
| Bulge in the main pulmonary artery |
| Ascites (collection of fluid in the abdominal
cavity) |
| Hepatomegaly (enlarged liver) |
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| EKG may show:
| Normal EKG |
| Right ventricular enlargement criteria with
moderate to severe pulmonic stenosis |
| Right atrial enlargement |
| May be normal with mild cases |
| Dysrhythmias may be noted |
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| Echocardiography:
| Right ventricular hypertrophy |
| Stenosis of the pulmonic valve |
| Increased velocity of flow across the
pulmonic valvular orifice by Doppler |
| Pulmonic regurgitation by Doppler |
| Right ventricular enlargement |
| Tricuspid regurgitation by Doppler
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For moderate to severe
pulmonic stenosis, the treatment of choice is surgery. However, the efficacy
of surgical intervention remains to be substantiated. Surgery is more risky
if atrial fibrillation or congestive heart failure has developed. These
conditions should be treated medically and the dog stabilized, before
surgery is considered.
A
relatively new technique is now being used, called Balloon Valvuloplasty. A
catheter with a small balloon on the end is guided to the position of the
narrowing during heart catheterization. The balloon is then inflated to open
the constriction. This procedure will reduce the morbidity and mortality
associated with thoracic surgery, it appears to be good in the short-term, but
long-term studies are needed.
| The prognosis for individuals with mild cases
of pulmonic stenosis is that they can be expected to live a full life with
this abnormality. |
For severe cases of pulmonic
stenosis the dog may die suddenly if acute dysrhythmias develops (sudden
death). Or the dog may develop signs of right sided heart failure and die in
6-12 months.
| 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. |
Links to sites about this disease:
Resources:
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Clinical Cardiology Concepts for
the Dog and Cat: Michael R. O’Grady DVM, MSc, Diplomate, ACVIM
(Cardiology) & Lynne O’Sullivan DVM, DVSc, Diplomate ACVIM
(Cardiology) – VetGo Cardiology.
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Pulmonic Stenosis: Provet
Healthcare Information.
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Pulmonic Stenosis: Alice Crook,
BSc, DVM & Brian Hill DVM, MS, DACVIM. University of Prince Edward
Island. Canine Inherited Disorders Database.
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This summary provided by:
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Olga I. Twombly
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WhiteFang Shilohs
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