Difference between revisions of "Aortic 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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*Common in dogs: especially subvalvular lesions; Boxers usually have valvular stenosis  
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*Rare in cats: usually they get supravalvular lesions
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===Signalment===
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Genetics & Predisposed Breeds: Newfoundland, Boxer, German Shepherd, Golden Retriever, Bull Terrier
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===Description===
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The three possible areas for aortic stenosis to occur:
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1. Subvalvular or subaortic (occurs below the valve)
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2. Valvular or aortic (occurs at the valve)
  
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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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3. Supravalvular (occurs after the valve)
  
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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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*The stenotic area is a consequence of fibrous tissue on and around the aortic valve
  
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==Signalment==
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*A narrowing of the aortic outflow tract causes an increase in pressure
  
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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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*Increased pressure leads to left ventricular dilation and concentric hypertrophy as a means of maintaining sufficient cardiac output
  
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== Clinical Signs ==
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*The severity of stenosis determines the extent of hypertrophy
  
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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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*Hypertrophy of the myocardium leads to an increased oxygen demand and decreased diastolic filling
  
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== Diagnosis  ==
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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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===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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*There is an increased risk of bacterial endocarditis in animals affected by this condition
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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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===Diagnosis===
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* Left ventricular enlargement may be recognised
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====History & Clinical Signs====
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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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-Weakness
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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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-Exercise Intolerance
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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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-Syncope
  
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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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-Stunting of Growth
  
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== Prognosis  ==
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-Pallor
  
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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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-Or may be asymptomatic
  
  
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== References  ==
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====Physical Exam====
  
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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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-Systolic murmur (Loudest over aortic valve)
  
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Fossum, T. W. et. al. (2013) Small Animal Surgery (fourth edition), Elsevier Mosby
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-Weak femoral pulses
  
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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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{{review}}
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====Radiographic Findings====
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-Left ventricular enlargement or bulge around the aortic valve
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-Radiographs may appear normal due to concentric hypertrophy
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====Electrocardiography (ECG)====
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-Increased R-wave amplitude (Indicates Left Ventricular Hypertrophy)
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-Ventricular Arrhythmias (Only Severely Affected Animals)
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====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
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===Treatment===
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Palliative Treatment=alleviate symptoms without curing disease
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-Exercise Restriction
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-B-Blockers (Prevent/Control Ventricular Arrhythmias)
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Surgical Treatment=currently poor outcome
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-Balloon Valvuloplasty
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===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
  
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[[Category:Cardiovascular_System_-_Developmental_Pathology]] [[Category:Expert Review]] [[Category:Cardiac_Diseases_-_Cat]] [[Category:Cardiac_Diseases_-_Dog]]
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-Sudden death within the first 1-3 years of life
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[[Category:Cardiology Section]]
 

Revision as of 10:44, 22 September 2008

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CARDIOLOGY
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  • 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

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