Pulmonic Stenosis

CARDIOLOGY ()Map CARDIOVASCULAR CONDITIONS (Map)

• 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