Aortic Stenosis

• 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.