Aortic Stenosis
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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