Difference between revisions of "Pulmonic Stenosis"

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== Introduction ==
 
== Introduction ==
  
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Pulmonic stenosis (PS) is one of the three most common congenital cardiac defects in dogs. It is much less common in cats, and is usually recognised in association with other congenital cardiac defects in this species.
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This is cardiovascular disease that is common in dogs and rare in cats and large animals.  
  
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Pulmonic stenosis may be '''subvalvular/infundibular'''  (occurs below the valve), '''valvular''' (occurs at the valve) or '''Supravalvular''' (occurs above the valve). '''Most '''cases of PS in the dog are '''valvular''', whilst supravalvular PS is rare. 
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The three possible areas for pulmonic stenosis to occur are:
  
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'''Subvalvular (infundibular)''' PS is defined as a fibrous or fibromuscular diaphragm below the pulmonic valve or at the os infundibulum, or a more diffuse and extensive area of fibromuscular hypertrophy creating more of a tunnel or hour-glass deformity of the infundibulum.
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1. '''Subvalvular''' or '''subpulmonic''' (occurs below the valve)
  
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'''Valvular''' PS can be further classified into type A or type B, based on valvular morphology. '''Type A''' cases have a '''normal pulmonary annulus diameter''' and '''type B''' cases have a '''narrow pulmonary annulus diameter''', often accompanied by hypoplasia of the pulmonary trunk. Type A cases are more likely to show a post-stenotic dilatation.
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2. '''Valvular''' (occurs at the valve)
  
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Concentric hypertrophy of the right ventricle develops as a consequence of the chronic pressure overload resulting from obstruction to right ventricular outflow. Right ventricular hypertrophy may cause an infundibular narrowing of the right ventricular outflow tract (RVOT), exacerbating the stenosis and resulting in a dynamic component to the obstruction. A further consequence of right ventricular hypertrophy is reduced right ventricular diastolic filling and therefore elevated right atrial pressures with resultant right atrial dilation.
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3. '''Supravalvular''' (occurs above the valve)  
  
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In '''Bulldogs''', PS may be complicated by '''coronary artery anomalies'''.
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'''Most '''cases of pulmonic stenosis are '''valvular''', whilst supravalvular pulomic stenosis is rare. Stenosis of the pulmonary outflow tract is the result of dysplastic changes in the pulmonic valve. Concentric hypertrophy of the right ventricle forms as a direct result of the chronic pressure overload needed to surpass the increased resistance from the stenotic pulmonary outflow tract. This concentric hypertrophy causes decreased ventricular filling during diastole and elevated right atrial pressure from the blood are unable to fill the ventricle causes atrial dilation. Tricuspid valve regurgitation can also be present and adds to the atrial pressure.
  
 
==Signalment==
 
==Signalment==
  
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Predisposed breeds of dog include the Miniature Schnauzer, Cocker Spaniel, Fox Terrier, Chihuahua, Miniature Pinscher, Labrador Retriever, Newfoundland, Mastiff, Boxer, Samoyed and English and French Bulldog.
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Predisposed breeds of dog include the Miniature Schnauzer, Fox Terrier, Chihuahua, Miniature Pinscher, Labrador Retriever, Newfoundland, Mastiff, Samoyeds and Terrier Breeds.  
  
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== History and Clinical Signs ==
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== Clinical Signs ==
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A murmur is usually detected at the initial health check or primary vaccination.
 
  
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Clinical signs include exercise intolerance, syncope and signs of [[Heart Failure, Right-Sided|right sided congestive heart failure]] (if severely affected). Animals may be asymptomatic.
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Exercise intolerance, syncope and signs of [[Heart Failure, Right-Sided|right sided congestive heart failure]] (if severely affected). Sometimes the condition can be asymptomatic if only mildly affected.  
  
 
== Diagnosis ==
 
== Diagnosis ==
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===Physical Examination===
 
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* Left-sided, systolic murmur with point of maximal intensity over the heart base
 
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* Grade of murmur correlates with severity of stenosis for fixed obstructions
 
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* Apex beat may be more palpable on the right hemithorax than the left if severe right ventricular hypertrophy is present.
 
  
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History and clinical signs can be indicative of heart disease. Upon physical examination, it is likely that a systolic crescendo-decrescendo ejection murmur over pulmonary artery in the left heart base will be heard. There will usually be normal femoral pulses. There may be signs of right sided congestive heart failure, such as ascites and jugular distension and jugular pulses.
  
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There may be signs of [[Heart Failure, Right-Sided|right sided congestive heart failure]], such as ascites and jugular venous distension and hepatojugular reflux.
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'''Radiographic''' findings may include right ventricular enlargement (DV view seen at 1 o'clock), right atrial enlargement and pulmonary artery enlargement (DV view seen at 2 o'clock). Changes are seen most clearly on the dorsoventral view.  
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===Thoracic Radiographs===
 
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Radiographic findings may include right ventricular enlargement (seen at 1 o'clock on a dorsoventral view), right atrial enlargement and pulmonary artery enlargement (seen at 2 o'clock on a dorsoventral view).  
 
  
 
'''Echocardiographic''' findings may include right ventricular hypertrophy, poststenotic dilation of the pulmonary artery and abnormal pulmonic valve if the stenotic area is valvular. Doppler can be used to measure the pressure in the stenotic area and visualize abnormal flow.
 
'''Echocardiographic''' findings may include right ventricular hypertrophy, poststenotic dilation of the pulmonary artery and abnormal pulmonic valve if the stenotic area is valvular. Doppler can be used to measure the pressure in the stenotic area and visualize abnormal flow.
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[[Category:Cardiovascular_System_-_Developmental_Pathology]] [[Category:Expert_Review]] [[Category:Cardiac_Diseases_-_Cat]] [[Category:Cardiac_Diseases_-_Dog]] [[Category:Cardiac_Diseases_-_Horse]]
 
[[Category:Cardiovascular_System_-_Developmental_Pathology]] [[Category:Expert_Review]] [[Category:Cardiac_Diseases_-_Cat]] [[Category:Cardiac_Diseases_-_Dog]] [[Category:Cardiac_Diseases_-_Horse]]
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[[Category:Cardiology Section]]
 

Revision as of 13:59, 19 October 2011

Introduction

This is cardiovascular disease that is common in dogs and rare in cats and large animals.

The three possible areas for pulmonic stenosis to occur are:

1. Subvalvular or subpulmonic (occurs below the valve)

2. Valvular (occurs at the valve)

3. Supravalvular (occurs above the valve)

Most cases of pulmonic stenosis are valvular, whilst supravalvular pulomic stenosis is rare. Stenosis of the pulmonary outflow tract is the result of dysplastic changes in the pulmonic valve. Concentric hypertrophy of the right ventricle forms as a direct result of the chronic pressure overload needed to surpass the increased resistance from the stenotic pulmonary outflow tract. This concentric hypertrophy causes decreased ventricular filling during diastole and elevated right atrial pressure from the blood are unable to fill the ventricle causes atrial dilation. Tricuspid valve regurgitation can also be present and adds to the atrial pressure.

Signalment

Predisposed breeds of dog include the Miniature Schnauzer, Fox Terrier, Chihuahua, Miniature Pinscher, Labrador Retriever, Newfoundland, Mastiff, Samoyeds and Terrier Breeds.

Clinical Signs

Exercise intolerance, syncope and signs of right sided congestive heart failure (if severely affected). Sometimes the condition can be asymptomatic if only mildly affected.

Diagnosis

History and clinical signs can be indicative of heart disease. Upon physical examination, it is likely that a systolic crescendo-decrescendo ejection murmur over pulmonary artery in the left heart base will be heard. There will usually be normal femoral pulses. There may be signs of right sided congestive heart failure, such as ascites and jugular distension and jugular pulses.

Radiographic findings may include right ventricular enlargement (DV view seen at 1 o'clock), right atrial enlargement and pulmonary artery enlargement (DV view seen at 2 o'clock). Changes are seen most clearly on the dorsoventral view.

Echocardiographic findings may include right ventricular hypertrophy, poststenotic dilation of the pulmonary artery and abnormal pulmonic valve if the stenotic area is valvular. Doppler can be used to measure the pressure in the stenotic area and visualize abnormal flow.

Electrocardiographic (ECG) signs include right ventricular hypertrophy (tall P waves, deep S waves, deep Q waves, right axis deviation).

Angiography may also be used to identify the defect.

Treatment

The pressure gradient between the right ventricle and the pulmonary artery can be used to decide between medical and surgical management.

In mild to moderate cases, if there are no clinical signs then no treatment is needed.

In severe cases, if the pressure gradient is greater than 100mmHg, an invasive procedure may need to be performed. Possible options for surgery include a balloon valvuloplasty (done if pulmonic leaflets are fused) or surgical repair (done when more complex lesions and obstructions are present): valvulotomy, pericardial patch graft.

If signs of right-sided heart failure are present, these should be managed medically with diuretics and vasodilators.

Prognosis

Mild to moderate cases have a good prognosis. Severe cases have a guarded prognosis.


Pulmonic Stenosis Learning Resources
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Flashcards
Test your knowledge using flashcard type questions 		Small Animal Soft Tissue Surgery Q&A 21


References

Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition) W.B. Saunders Company

Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2) W.B. Saunders Company

Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition) Mosby Elsevier


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