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