Shone’s Complex

Shone’s complex (also called Shone syndrome) is a type of congenital heart disease that affects blood flow on the left side of your baby’s heart. This side receives blood from their lungs and sends it out to the rest of their body. Multiple obstructions, also called lesions, make it harder for blood to move into and out of the lower left heart chamber (left ventricle). Your baby needs surgery to repair these issues and improve blood flow.

What conditions are associated with Shone’s complex?

Shone’s complex is named for the doctor who first described it in the 1960s. Dr. Shone identified four associated heart problems, but experts have since expanded the list. Babies with Shone’s complex have at least two of the following eight heart defects:

• Cor triatriatum: There’s an extra membrane in the top left chamber of your baby’s heart (left atrium). This divides the chamber into two sections. Blood has a harder time flowing down to the left ventricle.
• Supravalvular mitral ring: Your baby’s mitral valve has a ring of fibrous tissue just above it. That narrows the valve opening and limits blood flow from their left atrium to their left ventricle.
• Parachute mitral valve: Your baby’s mitral valve is missing a papillary muscle. These two muscles open and close the valve. Having just one can make the valve narrow or leaky. 
• Hypoplastic left ventricle: “Hypoplastic” means not fully developed. The left ventricle is the heart’s main pumping chamber. Being smaller means it can’t pump blood like it should.
• Subaortic stenosis: Your baby’s aortic valve is narrow because of extra tissue below it. Their heart must pump harder because of the narrowing.
• Bicuspid aortic valve: Your baby’s aortic valve has just two flaps rather than three. This can lead to problems like a narrow or leaky valve.
• Small aortic valve annulus: The tough ring at the base of your baby’s aortic valve is smaller than it should be. Less blood can flow through the valve into the aorta.
• Coarctation of the aorta: Your baby’s heart has to work harder because their aorta has a narrow spot.

Shone’s complex is rare. It accounts for about 1 in 50 congenital heart disease cases providers diagnose before birth.

Symptoms of Shone’s complex

In severe cases, symptoms can begin soon after birth. This is because your baby’s heart can’t pump enough blood to meet their body’s needs. Other times, signs and symptoms can develop later in childhood or even in adulthood. Your child may have:

• Difficulty gaining weight
• Sweating and trouble breathing when feeding
• A lower amount of pee than expected
• Weak pulses in their legs and arms
• Higher blood pressure in their arms than their legs
• A buildup of lactic acid in their blood

What causes Shone’s complex?

Healthcare providers don’t know exactly what causes Shone’s complex. Most cases are sporadic. We don’t yet have enough information on genetic or environmental risk factors to say for sure why some babies are born with this condition. 

Some research suggests Shone’s complex may be hereditary. But how it passes down within biological families is complex. We need more research to fully understand it.

Complications of this condition

Shone’s complex may cause complications like:

• High blood pressure in your child’s lung arteries (pulmonary hypertension)
• Abnormal heart rhythms, like heart block and atrial arrhythmias
• Your child’s heart not being able to pump blood like it should (heart failure)

How doctors diagnose this condition

Healthcare providers diagnose Shone’s complex using one or more of the following tests:

• Fetal echocardiogram: This test uses ultrasound to diagnose heart problems before birth.
• Transthoracic echocardiogram (TTE): This test also uses ultrasound to make images of your child’s heart. It’s the main way providers diagnose Shone’s complex after birth.
• Cardiac CT scan or MRI: Providers don’t routinely use these imaging scans to diagnose Shone’s complex, but they’re helpful in some cases.

Your baby’s provider will diagnose Shone’s complex if at least two of the eight possible defects are present. Babies with this condition usually have at least one lesion affecting blood flow into the left ventricle and at least one affecting blood flow out of it. Coarctation of the aorta is the most common feature.

Diagnosis usually happens before or soon after birth. But providers sometimes identify the condition for the first time in older children, teens and adults when they notice a heart murmur or other signs that lead to further testing. This can happen in people who have milder or incomplete forms of Shone’s complex. Cases diagnosed in older kids and adults are typically less severe but can still cause serious problems down the road.

How is Shone’s complex treated?

Surgery is the only way to treat Shone’s complex. There currently aren’t any medicines that can treat this condition. But your provider may prescribe medicines to manage your child’s symptoms or support their heart function until surgery.

There isn’t one surgery specific to Shone’s complex. Rather, providers choose the surgeries that meet your child’s needs. Exactly what happens during surgery depends on the heart defects your child has and how well their heart is working.

Your child may need one or more surgeries to:

• Remove the ring of tissue around their mitral valve
• Repair their mitral valve
• Replace their mitral valve (this is less common than repair)
• Remove extra tissue below their aortic valve
• Widen their aortic valve opening
• Repair the narrowed part of their aorta

Providers sometimes use a staged approach. That means your child will have two surgeries with some time in between them. The first surgery improves blood flow out of their left ventricle. The second improves blood flow into their left ventricle. Your child’s provider will explain how many surgeries your child may need and the best timing for them.

When should I seek medical care for my child?

It’s important to follow the appointment schedule your child’s provider gives you. Your child will need follow-up visits after each surgery. Their provider will run tests (echocardiograms) to check heart and valve function. These tests are key to finding and treating problems early.

Your child will need routine checkups with a cardiologist throughout their life.

Questions to ask

You may want to ask your child’s healthcare provider the following questions:

• What surgeries does my child need?
• What will happen during these surgeries?
• What follow-up care does my child need after surgery?
• How might Shone’s complex affect my child’s quality of life?

What is the prognosis for Shone’s complex?

Your child’s prognosis (outlook) depends on many things, including:

• The severity of their condition
• How soon they get treatment
• Any complications that arise
• Whether heart issues treated earlier in life come back

For example, coarctation of the aorta, narrowed valves and other features of Shone’s complex can recur. Your child may need more operations as they get older — even if treatment earlier in life worked. Your child’s providers can explain more based on their unique situation.

Shone’s complex survival rate

Most studies show long-term survival (up to 20 years) of at least 75% after surgery for Shone’s complex.

In general, Shone’s complex is more likely to shorten a person’s lifespan if:

• Their heart defects severely disrupt blood flow in their heart
• They need complex or multiple surgeries
• They develop severe mitral valve disease or pulmonary hypertension