Single Ventricle Defects

Single ventricle defects are rare and include a wide variety of congenital heart defects in which the heart has only one functional pumping chamber or ventricle.

About Single Ventricle Defects

A normal heart has two collecting chambers (atria) that receive blood and two pumping chambers (ventricles) that pump blood. A single ventricle heart defect occurs when the heart has only one ventricle that is large enough and strong enough to pump blood out to the rest of body. Patients with single ventricle heart defects have holes in the walls between either the ventricles or the atria that allow oxygen-rich blood to mix with oxygen-poor blood before being pumped out to the body. The poor circulation and inadequate oxygenation of the blood results in a bluish discoloration of the skin (cyanosis). The degree of cyanosis present is dependent upon the type of single ventricle defect present.

The most common single ventricle defects include:

• Tricuspid atresia occurs when the tricuspid valve between two of the heart's chambers isn't formed, and instead, there is solid tissue between the chambers that restricts blood flow.
• Pulmonary atresia with an intact ventricular septum occurs when the pulmonary valve is not formed, blocking the flow of blood from traveling directly from the right ventricle to the lungs.
• Mitral atresia occurs when the mitral valve does not develop properly and there is severe reduction or no blood flow from the left atrium to the left ventricle.
• Aortic atresia occurs when the aortic valve does not develop properly and there is no opening for blood to flow from the left ventricle to the aorta.
• Double inlet left ventricle occurs when the left and right atria of the heart are connected to the same ventricle.
• Hypoplastic left heart syndrome occurs when the left side of the heart is underdeveloped and not fully formed before birth.

Additionally, there are some children with congenital heart disease who technically have two ventricles; however, for various reasons, cannot have a biventricular repair and must down the single ventricle defect pathway.

Symptoms of Single Ventricle Defects

Symptoms related to single ventricle defects can vary depending on the type and severity of the defect.

Symptoms of single ventricle defects may include:

• Fast breathing
• Difficulty feeding
• Lethargy (sleepiness or unresponsiveness)
• Skin that appears pale or blue in color (cyanosis)
• Sweating during feeding

Diagnosing Single Ventricle Defects

Many single ventricle defects are diagnosed before the baby is born during routine ultrasound. Oftentimes, a referral to a fetal cardiologist is made and a fetal echocardiogram or ultrasound of your baby’s heart is performed. However, some patients may not be diagnosed until after birth.

During physical examinations, your child’s doctor listens to your child’s heart and lungs and may detect a heart murmur, which are extra sounds heard throughout the cardiac cycle due to increased blood flow. If your pediatrician suspects increased blood flow, a recommendation to see a pediatric cardiologist may be made. Your doctor may also refer you to a pediatric cardiologist if your child is breathing fast, has lips or skin that appear blue in color, has poor exercise tolerance (for babies, this includes poor feeding), or has an enlarged liver. Most babies with single ventricle defects require intensive intervention immediately after birth and a pediatric cardiologist is asked to evaluate the baby.

Tests performed when diagnosing single ventricle defects may include:

• Cardiac Catheterization: During cardiac catheterization, a small catheter (thin tube) is inserted into a larger blood vessel, typically in the groin, and guided to the heart where blood pressure and oxygen measurements can be taken in the aorta and pulmonary artery as well as the four chambers of the heart. A dye can also be injected through the tube to make the heart’s structure more visible on an X-ray.
• Cardiac MRI or CT Scan: A cardiac MRI or CT scan is used to take more detailed images of the heart to help define the anatomy and detect anomalies.
• Chest X-Ray: A chest X-ray produces an image of the tissue and bones in the heart and lungs and helps your provider assess the shape, size, and structure of the heart and lungs as well as the aeration of or any congestion in the lungs.
• Echocardiogram: An echocardiogram uses ultrasound technology to create a moving image of the heart and its valves, allowing your provider to assess the structure and function of the heart. An echocardiogram also helps provide information about blood flow and how well the heart is pumping blood.
• Electrocardiogram (ECG or EKG): An electrocardiogram uses electrodes that are placed on the body to record the electrical activity taking place in the heart. An ECG/EKG test helps detect abnormal rhythms, such as cardiac arrhythmias, stress on the heart, and damage to the heart muscles.

Treating Single Ventricle Defects

Most babies with single ventricle heart defects need treatment within the first few days to weeks of life to stabilize blood flow. Treatment of single ventricle defects is a staged approach.

Initial treatment options for single ventricle defects may include:

• Pulmonary Artery Banding: If there is too much blood flow to the lungs, the baby may need a pulmonary artery banding procedure to restrict the amount of blood traveling to the lungs.
• Blalock-Thomas-Taussig Shunt: If the baby does not have enough pulmonary blood flow to the lungs, they may need a Blalock-Thomas-Taussig shunt (BTT Shunt). During this procedure, a connection is made between the right subclavian artery (the first artery that branched off the aorta) and the right pulmonary artery. Some of the blood traveling through the aorta toward the body will "shunt" through this connection and flow into the pulmonary artery to receive oxygen.
• Cardiac Catheterization: If the baby does not have enough pulmonary blood flow to the lungs, using the same method as for diagnosis, a small tube can also be inserted through a blood vessel in the groin and guided to the heart where a stent can be placed in the ductus arteriosus (a blood vessel that connects the aorta and pulmonary artery) to also allow for increased blood flow.

The next stage of treatment typically involves the following:

• Glenn Procedure: Diverts half of the blood (the oxygen-poor blood coming back from the upper body) to the lungs. The shunt to the pulmonary arteries is disconnected and the pulmonary arteries are connected directly to the superior vena cava, the vein that brings deoxygenated blood from the upper part of the body to the heart. This sends half of the deoxygenated blood directly to the lungs without going through the ventricle. This procedure typically takes place between 4-6 months of age.
• Fontan Procedure: Connects the inferior vena cava, the blood vessel that drains deoxygenated blood from the lower part of the body into the heart, to the pulmonary artery by creating a channel through or just outside the heart. At this stage, all deoxygenated blood flows passively through the lungs. This typically takes place between 3-4 years of age.

Care Team Approach

The Texas Center for Pediatric and Congenital Heart Disease, a clinical partnership between Dell Children’s Medical Center and UT Health Austin, takes a multidisciplinary approach to your child’s care. This means your child and your family will benefit from the expertise of multiple specialists across a variety of disciplines. Your care team will include pediatric cardiologists, cardiothoracic surgeons, interventional cardiologists, critical care specialists, hospitalists, anesthesiologists, perfusionists, nurses, advanced practice providers, social workers, psychologists, child life specialists, dietitians, physical and occupational therapists, pharmacists, and more, who work together to provide unparalleled care for patients every step of the way. We collaborate with our colleagues at the Dell Medical School and The University of Texas at Austin to utilize the latest research, diagnostic, and treatment techniques, allowing us to identify new therapies to improve treatment outcomes. We are committed to communicating and coordinating your child’s care with referring physicians and other partners in the community to ensure that we are providing comprehensive, whole-person care.

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