Aortic Stenosis

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Category:WikiClinical CanineCow
Category:WikiClinical FelineCow
  • 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.