Pulmonic Stenosis

• Common in dogs

• Rare in cats

• Very rare in horses as an isolated abnormality; usually part of Tetralogy of Fallot

Signalment

Genetics & Predisposed Breeds: Most common in smaller breeds (Miniature Schnauzer, Fox Terrier, Chihuahua, Miniature Pinscher); Larger breeds are also affected (Labrador Retriever, Newfoundland, Mastiff, Samoyeds); Terrier Breeds are frequently affected

Description

The three possible areas for pulmonic stenosis to occur:

1. Subvalvular or subpulmonic (occurs below the valve)

2. Valvular (occurs at the valve)

3. Supravalvular (occurs above the valve)

• Stenosis of the pulmonary outflow tract is the result of dysplastic changes in the pulmonic valve

• Most cases of pulmonic stenosis are valvular

• Supravalvular pulmonic stenosis is rare

• Concentric hypertrophy of the right ventricle forms as a direct result of the chronic pressure overload needed to surpass the increased resistance from the stenotic pulmonary outflow tract

• Concentric hypertrophy causes decreased ventricular filling during diastole

• Elevated right atrial pressure from the blood unable to fill the ventricle causes atrial dilation

• Tricuspid valve regurgitation can also be present and adds to the atrial pressure

• In addition to the diagnostic methods listed below, angiography may be used to show the defect

Diagnosis

History & Clinical Signs

-Exercise Intolerance

-Syncope

-Signs of right sided congestive heart failure (severely affected)

-Asymptomatic (mildly affected)

Physical Exam

-Systolic ejection murmur over pulmonary artery in the left heart base

-Usually normal femoral pulses

-Signs of right sided congestive heart failure may be present:

• ascites

• jugular distension & jugular pulses

Radiographic Findings

-Right ventricular enlargement (DV view seen at 1 o'clock)

-Right atrial enlargement

-Pulmonary artery enlargement (DV view seen at 2 o'clock)

(Changes are seen the most clearly on a dorsoventral view)

Echocardiographic Findings

-Right ventricular hypertrophy

-Poststenotic dilation of the pulmonary artery

-Abnormal pulmonic valve if the stenotic area is valvular

Doppler can be used to measure the pressure in the stenotic area and visualize abnormal flow

Electrocardiographic (ECG)

-Right ventricular hypertrophy (deep S waves, right axis deviation)

Treatment

Mild/Moderate Cases

-If there are no signs, no treatment is needed

Severe Cases

-Animals that exhibit many of the clinical signs will need further treatment

• Balloon valvuloplasty (done if pulmonic leaflets are fused)

• Surgical repair (done when more complex lesions & obstructions are present): valvulotomy, pericardial patch graft

Prognosis

Mild/Moderate Cases

-Good prognosis

Severe Cases

-Guarded prognosis

From Pathology

Obstructs blood flowing form the right ventricle to the pulmonary artery. As with aortic stenosis may be subvalvular, valvular or supravalvular. Valvular stenosis is the most common form in the dog.

Incidence:

• Increased incidence in English bulldogs, Cocker spaniels, Chihuahuas.
• Autosomal dominant in Beagles.

Clinical Signs:

• Asymptomatic if mild or moderate.
• If severe; exercise intolerance, stunting, syncope, right sided heart failure E.g. ascites.
• Harsh systolic murmur at left heart base.
• May hear splitting of the second heart sound due to delayed closure of the pulmonic valve.
• Femoral pulse quality good but jugulars distended.

Diagnosis:

• Right ventricular enlargement on radiology, along with post-stenotic dilatation of the pulmonary artery and pulmonary undercirculation.
• Abnormal valve can be imaged using echocardiography.
• Severity of stenosis can be assessed using Doppler to calculate flow rates.

Treatment:

• Balloon valvuloplasty is treatment of choice.