What is pulmonic stenosis in dogs, and can it be fixed? 

Pulmonic stenosis (also called pulmonary stenosis) is a serious condition of the heart. It is often congenital, meaning your dog is born with it, and the first indication of a problem may be when a heart murmur is picked up during a routine puppy check by your vet. Being told your dog has a heart murmur is always going to be a heart dropping moment at any age, let alone in a young puppy. What is causing it and what does this mean for your dog? There are several reasons dogs may have heart murmurs, ranging from harmless, self-correcting issues to more serious underlying heart problems such as pulmonic stenosis. Keep reading for the full scoop on this condition.  

What is pulmonic stenosis? 

Pulmonic stenosis is one of the more common congenital (meaning present at birth) heart defects in dogs. In rare cases, pulmonic stenosis can develop later in life due to inflammation, infection, or tumours affecting the heart or surrounding structures. However, most cases of pulmonic stenosis are congenital. 

Regardless of the underlying cause, pulmonic stenosis is a narrowing of the pulmonary valve, which connects the right side of the heart to the pulmonary artery. The pulmonary artery carries blood from the heart to the lungs, where it picks up oxygen and then travels back to the heart. The heart then pumps the oxygen rich blood around the rest of the body where it is needed. The narrowing in the pulmonary valve creates a partial blockage in the blood flow from the heart to the lungs. A bit like a dam in a river, this leads to a ‘backlog’ of blood in the heart, behind the valve. Pulmonic stenosis essentially causes two problems: 

1. The heart gets stretched due to the extra volume of blood in it, increasing the pressure in the right side of the heart. 

2. The lungs receive less blood from the heart because of the partial blockage in the narrowed pulmonary valve.  

Why does it happen? 

The narrowing (or stenosis) can be present due to abnormalities in the pulmonary valve itself (e.g. if it is fused or malformed), abnormalities in the heart tissue just below the valve, or abnormalities just above the valve in the pulmonary artery. In all cases, the overall effect is a narrowing and restriction of the blood flow through the valve to the lungs.  

Breeds commonly affected with pulmonic stenosis include: 

Because pulmonic stenosis can be inherited in these breeds, responsible breeders may screen for it to avoid passing it on to puppies. 

What are the signs of pulmonic stenosis in my dog? 

In mild or early cases, outward signs of pulmonic stenosis may not be present, but it can worsen over time and eventually lead to heart failure. The symptoms of pulmonic stenosis will vary depending on the severity of the narrowing and how hard the heart must work to compensate. In more severe cases, symptoms can include: 

Since dogs can be quite good at masking their symptoms, especially in the early stages, many cases are first identified when your vet hears a murmur during a routine exam. Because most cases of pulmonic stenosis are congenital, heart murmurs can be detected in young puppies, maybe during their first vet check. There are many causes of heart murmurs in puppies, and not all murmurs are serious, but they are often a clue that further investigation is needed. 

How is pulmonic stenosis diagnosed in dogs? 

You may notice some of the above symptoms in your dog, but more commonly the first sign is often a heart murmur picked up by your vet during a routine clinical exam. Because there are many different reasons your dog may have a heart murmur, further diagnostic tests will be needed to reveal whether the underlying cause is pulmonic stenosis or a different heart condition.  

1. Physical examination – the vet will listen to your dog’s heart with a stethoscope. A loud murmur heard on the right side of the chest is a common finding in pulmonic stenosis. 

2. Echocardiogram (an ultrasound of the heart) – this is the most definitive way to diagnose pulmonic stenosis. It allows the vet to visualise the structure of the heart, measure the degree of narrowing, and assess how the heart is functioning overall. 

3. Chest X-rays – these may show an enlarged right side of the heart or changes in the lungs if the condition has progressed. 

4. Electrocardiogram (ECG) – this can detect abnormal heart rhythms, which may occur in more advanced cases of pulmonic stenosis.  

Can it be fixed? 

Many dogs live happily with a mild pulmonic stenosis not causing any outward problems. In these cases, your vet will recommend regular monitoring to ensure any progression of the disease is caught early. With more severe cases, treatment may be indicated. Unfortunately, a cure is not possible. Treatment is aimed at improving your dog’s quality of life and reducing the risk of complications, rather than providing a complete cure. 

Treatment options may include: 

1. Balloon valvuloplasty 

This is a minimally invasive surgical procedure that is performed by a specialist veterinary cardiologist. A catheter with a small balloon at its tip is inserted into a vein and guided into the heart. Once it reaches the narrowed pulmonary valve, the balloon is inflated to stretch the valve open and improve blood flow. A balloon valvuloplasty can significantly reduce the pressure on the right side of the heart, relieving symptoms and improving quality of life. It can also reduce the risk of sudden death by 53%. Some dogs may need repeat procedures if the valve re-narrows over time. 

2. Medication 

Medication like beta-blockers can help manage symptoms by reducing the heart’s workload, slowing the heart rate and lowering blood pressure. They are commonly used when a balloon valvuloplasty is not possible, or alongside surgery. Pulmonic stenosis can eventually lead to right sided heart failure and/or arrythmias, and medications can also be used to ease symptoms if this develops. 

What is the prognosis? 

Dogs with mild pulmonic stenosis often live a full, normal life. Those with moderate to severe cases can also do well, especially if treated early and appropriately. However, without treatment, severe pulmonic stenosis can lead to right-sided heart failure, arrhythmias, or sudden death. 

Summary 

Pulmonic stenosis is usually congenital i.e. it develops because of a heart abnormality that your dog is born with. It is often picked up in puppies or young dogs, but may also develop later in life due to other causes. If your dog is from a breed known to be at risk, regular veterinary check-ups and monitoring is sensible to catch any changes early. Pulmonic stenosis can be serious, but if it is detected early and monitored well, most cases can be well managed. Even in the more serious cases, advancements in veterinary cardiology have made it possible for many dogs to live long, active lives with proper diagnosis and treatment.