At Additional Ventures, our mission is to cure single ventricle heart disease through transformative research and strategic investments that revolutionize treatment and care. We’re committed to finding new and better treatments and developing cures for all patients, no matter their age, stage, or experience.

Single ventricle heart disease affects about 35 out of every 100,000 newborns in the US. There has been huge progress in its treatment over the last 50 years, but there is so much more to do. We believe that single ventricle heart disease is a solvable problem and we see a future where cures are available for single ventricle patients.

Here, you will find more information about single ventricle heart disease, why more research is needed, and details of our Research Roadmap for solving this complex and challenging disease.

Single ventricle heart disease, also called a single ventricle heart defect, is a type of congenital heart problem. In other words, people with single ventricle are born with it. Most single ventricle hearts can be detected on a 20-week pregnancy scan or after birth by echocardiogram (ECG).

Having a single ventricle heart defect means one ventricle does not form properly when the embryo or fetus is developing in the uterus. For example, one ventricle may be too small or may be missing a valve. With only one ventricle working well, patients with single ventricle heart disease cannot get enough oxygen from their lungs to the rest of their bodies. As a result, children with single ventricle heart defects may appear blue.

While scientists don’t yet fully understand why single ventricle heart disease happens, it is likely caused by many different factors, including a person’s genes. In 2024, Additional Ventures launched Single Ventricle SOURCE, a first-of-its-kind study that will help researchers uncover the specific causes of single ventricle.

Treatments for Single Ventricle Heart Disease

Single ventricle heart disease is fatal if it is not treated. There are two types of treatments that allow someone with a single ventricle heart defect to live with the disease: palliative heart surgery and heart transplant. Both options come with many risks and require one or more open heart surgeries, often in very young babies and children.

These treatments are life-saving, but they are not cures. They also create lifelong challenges that can alter a person’s quality of life and lifespan.

Heart Surgery

Most babies born with single ventricle heart disease have a series of two to three open heart surgeries, starting at a few days old. The goal of these surgeries is to make sure the blood that gets pumped through the body has enough oxygen in it. The series of surgeries — sometimes called “staged reconstruction” — can include the Norwood, Glenn, and Fontan procedures, and/or placement of bands or shunts that change the amount or direction of blood flow.

The Fontan procedure is usually carried out when the child is between two and six years old. The goal of the Fontan is to redirect blood flow from the lower body directly to the lungs, without passing through the heart. This allows the child’s one working ventricle to handle only oxygen-rich blood and pump it to the rest of the body.

While the Fontan procedure is beneficial for single ventricle patients, it can also cause many complications over time, such as blood clots and problems with heart rhythm (arrhythmias) and liver function, to name a few.

Heart Transplant

Some single ventricle patients require a heart transplant. A heart transplant can happen at different stages of a patient’s journey — for example, immediately after birth or at any time during or after the series of palliative surgeries if their heart is not healthy enough.

Patients who get a heart transplant will need to take certain medications for the rest of their lives to make sure their body does not reject the new heart. These medications lower the body’s ability to fight infections and can also cause serious side effects, but they are important for a successful transplant. Some patients may need to be re-transplanted in the future.

Everyone’s heart transplant journey looks different and can be affected by factors like how long they are on the waiting list for a transplant, availability of donor hearts, and the patient’s health status before or after a transplant.

More research is needed

A diagnosis of single ventricle heart disease used to mean a child would not live long. Most patients now survive into adulthood, thanks to available treatments. But even with these treatment options and, in some ways, because of them, patients experience a range of issues that impact both their quality and duration of life, even into adulthood.

More research is needed to understand what causes single ventricle heart disease and the many related complications. With more knowledge, scientists can improve existing treatments, develop better treatments, and even develop cures.

Our Research Roadmap helps us understand and map out what research and information is needed to reach these goals. To create this Roadmap, we worked collaboratively with the research and clinical community.

Interviewed more than 200 experts

Reviewed existing scientific and medical research

Identified research gaps and needs

Formed expert working groups that designed ways to overcome these gaps