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Balloon Valvuloplasty for Canine Pulmonic Stenosis

Written By:

Nick A. Schroeder, DVM, DACVIM
Cardiology

Dogs that have congenital pulmonic stenosis (PS) have a narrowed outflow of the right side of the heart. When this results from fusion of the pulmonic valve leaflets, these patients may benefit from a palliative catheter-based procedure called balloon valvuloplasty.

Dogs are diagnosed with PS using the history, physical examination and complete echocardiography (cardiac ultrasound). In some cases, thoracic radiographs and EKG are useful, but not diagnostic. The ideal candidate for balloon valvuloplasty has severe PS as determined by echocardiography with mild secondary right heart muscle thickening and fusion of the commisures of the pulmonic valve leaflets. Patients that have mild-moderate PS may not require ballooning and are often asymptomatic. Patients with severe heart muscle thickening may not benefit as much from the procedure, which may be technically more difficult in such cases. Patients with pulmonic valvular dysplasia with thickened and immobile leaflets are less likely to benefit from balloon valvuloplasty. Some patients have associated coronary anomalies or multiple congenital defects and balloon valvuloplasty may unfortunately not be an option in these cases.

 

Chest x-rays from a dog with severe pulmonic stenosis. The right side of the heart is a little enlarged and a prominent bulge is present from enlargement of the main pulmonary artery.

Echocardiographs from a patient with severe pulmonic stenosis. To the left, the right side of the heart is enlarged and there is severe thickening of the right ventricle. To the right, Doppler technology allows us to estimate the pressure drop across the pulmonic valve. The blood is ejected across the pulmonic valve at a very high velocity, indicating severe stenosis (narrowing).
Echocardiograph of another dog with pulmonic stenosis. The valve leaflets are domed and fused, making this dog a good candidate for balloon valvuloplasty. Color flow Doppler allows us to see that the valve also leaks.
Angiogram of a dog with a coronary artery malformation. Dye is injected into the aortic root, allowing the small coronary arteries to fill. This must be done in breeds with pulmonic stenosis that commonly have associated coronary arterial malformation. Balloon valvuloplasty in this dog could be fatal, so this patient was medically managed.

Balloon valvuloplasty is performed under general anesthesia. Fluoroscopy (real-time x-ray) is utilized to allow visualization of the catheters within the heart. A small incision is made over one of the jugular veins, and a catheter is introduced and advanced into the right side of the heart. Intracardiac pressure measurements are taken. Dye is injected to allow us to visualize where the narrowed pulmonic valve is, and a balloon is advanced across this region. The balloon is then inflated with dye and stretches the leaflets of the valve apart. Pressure measurements are taken following the procedure. At least a 50% reduction in the pressure gradient is what we strive for. The small incision over the jugular vein is closed and stitches are typically removed in 10-14 days, at which time recheck echocardiography may be performed. Most patients stay overnight and go home the next day.

EKG and pressure tracing from a dog prior to balloon valvuloplasty. The pressure in the right ventricle is approximately 75 mmHg.

Some patients require medication following the procedure. Rechecks will be scheduled to monitor the heart disease and to look for any new problems. Many dogs experience a significant improvement in their exercise capacity following balloon valvuloplasty. Your veterinary cardiologist can help evaluate your pet to determine if they are a good candidate for the procedure.