Difference between revisions of "Aortic Stenosis"

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*Common in dogs: especially subvalvular lesions; Boxers usually have valvular stenosis  
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== Introduction ==
 
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Aortic stenosis is a congenital narrowing of the aortic valve, aorta or left ventricular outflow tract (LVOT).
 
  
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The three possible areas for aortic stenosis to occur are '''subvalvular or subaortic''' (occurs below the valve), '''valvular or aortic''' (occurs at the valve) and '''supravalvular''' (occurs after the valve). The most common form is subaortic stenosis (SAS), usually as a consequence of fibrous bands that may be circumferential (severe) or may only affect a small area of the LVOTO. The subvalvular fibrous ring may encompass the anterior mitral valve leaflet, causing it to become immobile.  In subaortic stenosis, the lesions may not be present from birth and may develop or progress as the dog matures; but do not generally progress beyond early adulthood. This is in contrast to valvular aortic stenosis, where the valve may become more stenotic as the dog ages.
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*Rare in cats: usually they get supravalvular lesions  
  
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Aortic stenosis causes an impedence to left ventricular ejection and consequent pressure overload of the left ventricle. The increase in afterload results in a compensatory ''''concentric left ventricular hypertrophy'''' in attempt to maintain sufficient cardiac output. The severity of stenosis usually determines the extent of hypertrophy. The myocardial hypertrophy results in increased myocardial oxygen demand, beyond the capacity of the coronary capillary vascular bed to supply oxygen. Increased wall stress also compromises coronary perfusion, particularly to the subendocardium. Insufficient oxygen supply to meet the needs of the hypertrophied left ventricle causes myocardial ischaemia and predisposes the animal to ventricular [[:Category:Arrhythmia|arrhythmias]].
 
  
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There is also an increased risk of bacterial [[Endocarditis|endocarditis]] in animals affected by this condition.
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===Signalment===
  
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==Signalment==
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Genetics & Predisposed Breeds: Newfoundland, Boxer, German Shepherd, Golden Retriever, Bull Terrier
  
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Aortic stenosis is one of the three most common congenital cardiac defects in dogs. Predisposed breeds include the Newfoundland, Boxer, German Shepherd, Golden Retriever and Bull Terrier. Boxers usually have valvular stenosis.
 
  
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== Clinical Signs ==
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===Description===
  
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Patients may present with exercise intolerance or syncope. However, the disease may be asymptomatic. Lack of clinical signs is not an appropriate reason to delay further investigation of a murmur, as sudden death can be the first indication of aortic stenosis.
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The three possible areas for aortic stenosis to occur:
  
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== Diagnosis  ==
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1. Subvalvular or subaortic (occurs below the valve)
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===Physical Examination===
 
  
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* Left sided, systolic [[Heart Murmurs|murmur]] with point of maximum intensity at the left base with radiation to the right base and thoracic inlet. The murmur grade usually correlates with the severity of the stenosis for fixed obstructions. The disease has a wide spectrum of severity, and low grade murmurs may be difficult to distinguish from physiological murmurs in puppies.
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2. Valvular or aortic (occurs at the valve)
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* Weak or hypokinetic femoral pulses in severe cases
 
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===Thoracic Radiographs===
 
  
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* May be unremarkable
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3. Supravalvular (occurs after the valve)
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* Left ventricular enlargement may be recognised
 
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* Post-stenotic dilatation of the aorta (bulge) on a dorsoventral view
 
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===Electrocardiography (ECG)===
 
  
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* Often unremarkable
 
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* Increased R wave amplitude and prolonged QRS duration (indicates left ventricular hypertrophy)
 
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* Ventricular premature complexes may be present in severe cases, due to myocardial hypoxia and ischaemia.
 
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===Echocardiography===
 
  
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* Left ventricular hypertrophy
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*The stenotic area is a consequence of fibrous tissue on and around the aortic valve  
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* Structural abnormality of the aortic valve or LVOT with or without a post-stenotic dilatation of the ascending aorta
 
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* Maximum aortic velocity >2.25m/s, turbulent flow (Doppler)
 
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* Trans-stenotic pressure gradient: mild <50mmHg, moderate 50-75mmHg, severe >75mmHg (Doppler)
 
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== Management ==
 
  
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The requirement for treatment is dictated by clinical signs and/or disease severity. Palliative treatment is usually the treatment of choice. It will attempt to alleviate symptoms without curing disease. Methods include exercise restriction and beta-blockers for prevention or control of [[:Category:Arrhythmia|arrhythmias]].
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*A narrowing of the aortic outflow tract causes an increase in pressure
  
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Surgical intervention has been described, but offers no advantage over medical therapy in most cases. Surgery should be considered for dogs with severe stenosis and marked left ventricular hypertrophy. In such cases, surgery should be performed early to minimize ischaemic changes to the myocardium. Surgical options for subaortic stenosis include valve dilation via baloon valvuloplasty or open resection under cardiopulmonary bypass.
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*Increased pressure leads to left ventricular dilation and concentric hypertrophy as a means of maintaining sufficient cardiac output
  
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== Prognosis  ==
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*The severity of stenosis determines the extent of hypertrophy
  
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The majority of cases are mild, do not require treatment and patients are likely to have a normal lifespan. In severe cases, there is often a poor quality of life. Complications from development of congestive [[Heart Failure|heart failure]] or cardiac [[:Category:Arrhythmia|arrhythmias]] can occur, as can sudden death.
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*Hypertrophy of the myocardium leads to an increased oxygen demand and decreased diastolic filling
  
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*Insufficient oxygen to meet the new needs of the hypertrophied left ventricle predisposes the animal to ventricular arrhythmias
  
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== References  ==
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*There is an increased risk of bacterial endocarditis in animals affected by this condition
  
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Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (sixth edition, volume 2), W.B. Saunders Company
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===Diagnosis===
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====History & Clinical Signs====
  
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Fossum, T. W. et. al. (2013) Small Animal Surgery (fourth edition), Elsevier Mosby
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-Weakness
  
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Luis Fuentes, V, Johnson, L.R, Dennis, S. (2010) BSAVA Manual of Canine and Feline Cardiorespiratory Medicine (second edition)
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-Exercise Intolerance
  
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{{review}}
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-Syncope
  
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{{OpenPages}}
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-Stunting of Growth
  
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-Pallor
  
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[[Category:Cardiovascular_System_-_Developmental_Pathology]] [[Category:Expert Review]] [[Category:Cardiac_Diseases_-_Cat]] [[Category:Cardiac_Diseases_-_Dog]]
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-Or may be asymptomatic
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[[Category:Cardiology Section]]
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 +
 
 +
====Physical Exam====
 +
 
 +
-Systolic murmur (Loudest over aortic valve)
 +
 
 +
-Weak femoral pulses
 +
 
 +
 
 +
====Radiographic Findings====
 +
 
 +
-Left ventricular enlargement or bulge around the aortic valve
 +
 
 +
-Radiographs may appear normal due to concentric hypertrophy
 +
 
 +
 
 +
====Electrocardiography (ECG)====
 +
 
 +
-Increased R-wave amplitude (Indicates Left Ventricular Hypertrophy)
 +
 
 +
-Ventricular Arrhythmias (Only Severely Affected Animals)
 +
 
 +
 
 +
====Echocardiography====
 +
 
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-Left ventricular concentric hypertrophy
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-Fibrous Tissue around aortic valve
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 +
-Dilation ascending aorta
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-Dilation of the left atrium
 +
 
 +
 
 +
===Treatment===
 +
 
 +
Palliative Treatment=alleviate symptoms without curing disease
 +
 
 +
-Exercise Restriction
 +
 
 +
-B-Blockers (Prevent/Control Ventricular Arrhythmias)
 +
 
 +
Surgical Treatment=currently poor outcome
 +
 
 +
-Balloon Valvuloplasty
 +
 
 +
 
 +
===Prognosis===
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'''Mild to Moderate SAS:'''
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-Normal quality of life if there is no progression of the malformation
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'''Severe SAS:'''
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-Poor quality of life
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-Complications from development of congestive heart failure or cardiac arrhythmias
 +
 
 +
-Sudden death within the first 1-3 years of life
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==From Pathology==
 +
 
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Obstructs blood flow from the left ventricle to the aorta.  Stenosis may be:
 +
*Subvalvular (most common in dog and cat).
 +
*Valvular.
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*Supravalvular.
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Subvalvular stenosis results in a jet of blood hitting the aortic valve, leading to damage and increased risk of developing endocarditis.
 +
 
 +
''Incidence:''
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*Increased prevalence in Boxers and Golden retrievers.
 +
*Autosomal dominant in Newfoundlands.
 +
 
 +
''Clinical Signs:''
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*Vary from asymptomatic to degrees of exercise intolerance, syncope and even sudden death.
 +
*Harsh systolic murmur at left heart base.
 +
Grade correlates with grade of murmur.
 +
High grade murmurs also have a precordial thrill.
 +
*Murmur may have a diastolic component due to aortic valve damage and insufficiency.
 +
*Weak femoral pulse.
 +
 
 +
''Diagnosis:''
 +
*Left ventricular enlargement on radiology and ECG.
 +
*Post-stenotic dilatation of the aorta may be visible on radiographs.
 +
*Echogenic fibrous ring may be seen on echocardiography.  Again, Doppler is useful to detect flow rates.
 +
 
 +
''Treatment:''
 +
*'''Balloon valvuloplasty'''; often unsuccessful.
 +
*Mild cases need no management.
 +
*Medical management; Beta-blockers to decrease myocardial oxygen consumption.
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*Prognosis guarded, death due to arrythmias in abnormal myocardium.
 +
 
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[[Category:Cardiovascular_System_-_Developmental_Pathology]][[Category:To_Do_-_Cardiovascular]]
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[[Category:Cardiac Diseases - Cat]][[Category:Cardiac Diseases - Dog]]

Revision as of 15:38, 20 December 2010

  • Common in dogs: especially subvalvular lesions; Boxers usually have valvular stenosis
  • Rare in cats: usually they get supravalvular lesions


Signalment

Genetics & Predisposed Breeds: Newfoundland, Boxer, German Shepherd, Golden Retriever, Bull Terrier


Description

The three possible areas for aortic stenosis to occur:

1. Subvalvular or subaortic (occurs below the valve)

2. Valvular or aortic (occurs at the valve)

3. Supravalvular (occurs after the valve)


  • The stenotic area is a consequence of fibrous tissue on and around the aortic valve
  • A narrowing of the aortic outflow tract causes an increase in pressure
  • Increased pressure leads to left ventricular dilation and concentric hypertrophy as a means of maintaining sufficient cardiac output
  • The severity of stenosis determines the extent of hypertrophy
  • Hypertrophy of the myocardium leads to an increased oxygen demand and decreased diastolic filling
  • Insufficient oxygen to meet the new needs of the hypertrophied left ventricle predisposes the animal to ventricular arrhythmias
  • There is an increased risk of bacterial endocarditis in animals affected by this condition

Diagnosis

History & Clinical Signs

-Weakness

-Exercise Intolerance

-Syncope

-Stunting of Growth

-Pallor

-Or may be asymptomatic


Physical Exam

-Systolic murmur (Loudest over aortic valve)

-Weak femoral pulses


Radiographic Findings

-Left ventricular enlargement or bulge around the aortic valve

-Radiographs may appear normal due to concentric hypertrophy


Electrocardiography (ECG)

-Increased R-wave amplitude (Indicates Left Ventricular Hypertrophy)

-Ventricular Arrhythmias (Only Severely Affected Animals)


Echocardiography

-Left ventricular concentric hypertrophy

-Fibrous Tissue around aortic valve

-Dilation ascending aorta

-Dilation of the left atrium


Treatment

Palliative Treatment=alleviate symptoms without curing disease

-Exercise Restriction

-B-Blockers (Prevent/Control Ventricular Arrhythmias)

Surgical Treatment=currently poor outcome

-Balloon Valvuloplasty


Prognosis

Mild to Moderate SAS:

-Normal quality of life if there is no progression of the malformation

Severe SAS:

-Poor quality of life

-Complications from development of congestive heart failure or cardiac arrhythmias

-Sudden death within the first 1-3 years of life

From Pathology

Obstructs blood flow from the left ventricle to the aorta. Stenosis may be:

  • Subvalvular (most common in dog and cat).
  • Valvular.
  • Supravalvular.

Subvalvular stenosis results in a jet of blood hitting the aortic valve, leading to damage and increased risk of developing endocarditis.

Incidence:

  • Increased prevalence in Boxers and Golden retrievers.
  • Autosomal dominant in Newfoundlands.

Clinical Signs:

  • Vary from asymptomatic to degrees of exercise intolerance, syncope and even sudden death.
  • Harsh systolic murmur at left heart base.

Grade correlates with grade of murmur. High grade murmurs also have a precordial thrill.

  • Murmur may have a diastolic component due to aortic valve damage and insufficiency.
  • Weak femoral pulse.

Diagnosis:

  • Left ventricular enlargement on radiology and ECG.
  • Post-stenotic dilatation of the aorta may be visible on radiographs.
  • Echogenic fibrous ring may be seen on echocardiography. Again, Doppler is useful to detect flow rates.

Treatment:

  • Balloon valvuloplasty; often unsuccessful.
  • Mild cases need no management.
  • Medical management; Beta-blockers to decrease myocardial oxygen consumption.
  • Prognosis guarded, death due to arrythmias in abnormal myocardium.
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