Childrens Hospital of Philadelphia: Treating Single Ventricle Defects

Approximately 3,000 U.S. children are born annually with severe heart defects in which one ventricle is too small or weak to pump effectively. While a single ventricle defect is not the most common birth abnormality, it is one of the most challenging due to its surgical complexity and high morbidity and mortality rate. As a result, high-volume facilities, such as the Children’s Hospital of Philadelphia (CHOP), have developed strategic programs to better manage and treat such patients.

Diagnosis

“One of the greatest unmet needs in pediatric cardiology is the care of patients with congenital heart disease, particularly the subset with single ventricle defects,” says Robert J. Levy, MD, the William J. Rashkind chair in pediatric cardiology and director of pediatric research at CHOP. “These children require critical care immediately, multiple surgeries very early in life and have very high rates of morbidity and mortality.”

As of the late 1970s, single ventricle defects—an umbrella term for several congenital heart defects—were 100 percent fatal, explains Levy, noting that while survival has improved, it is still one of the most difficult disease states to treat. The increased survival of these children has created a whole new population of adolescent and adult patients with unique needs that require increased resources to assist with a better quality of life.

Improvements in fetal echocardiography technology have aided in diagnosing this patient population. A decade ago, the condition was most often detected after birth in the newborn nursery or following discharge at home through a variety of symptoms, including blue skin or lips, a heart murmur or rapid heart rate. Some children would rapidly deteriorate, or even die shortly after birth, prior to diagnosis. 

“Today, most of our recommendations, counseling sessions and fetal anatomy identification take place prior to birth, which eases the management of the child and the mother,” says Jack Rychik, MD, director of the Fetal Heart Program at CHOP.

To standardize the procedural care response, Rychik and his colleagues created a grading scale to define, before birth, the level of care a newborn would require. For the most critical cases, Rychik and his team created the multidisciplinary IMPACT (IMmediate Post-partum Access to Cardiac Therapy) program, which dictates they be delivered by C-section with a cath lab team and OR team present to intervene within minutes.

Some institutions have begun performing catheter-based treatments in utero; however, the clinical results are still mixed with this approach and the longer-term outcomes remain unknown. “We have yet to confidently identify the natural history of cardiac lesions in utero. Until it’s better defined, we must carefully consider the risks and benefits of fetal intervention, even if the techniques are available,” says Rychik.

Evolving research 

In a trial sponsored by the Pediatric Heart Network (PHN) of the National Heart, Lung and Blood Institute, heart surgeons from 15 centers studied the outcomes in 549 newborns who received surgery for hypoplastic left heart syndrome (HLHS) in the newborn period and published their findings in the Single Ventricle Reconstruction (SVR) trial (N Engl J Med 2010;362(62):1980-1992). CHOP enrolled 101 subjects in the study.

The study assessed which of two types of shunts had better outcomes over the first year of life—the traditional surgical approach of a modified Blalock-Taussig shunt (MBTS; 275 patients), which carries blood from an artery branching off the aorta to the pulmonary artery, or a newer technique, known as the right ventricle-pulmonary artery shunt (RVPA; 274 patients), which links the right ventricle to the pulmonary artery. If either technique fails, the only life-saving alternative is a heart transplant.

One year after the surgery, 74 percent of infants with the RVPA shunt survived and didn't require a heart transplant, compared to 64 percent of infants with the MBTS. However, the RVPA group had a higher rate of complications requiring unanticipated interventions, such as stents or balloons to keep the shunt open. After the first year, rates for transplantation-free survival were the same for both arms.

“This was the first multi-institutional randomized, clinical trial of a surgical technique in pediatric heart disease,” says J. William Gaynor, MD, a pediatric cardiothoracic surgeon at CHOP, who served as the study’s senior author and co-principal investigator. “The one-year outcome, however, is most likely too early to provide a definitive answer as to which type of shunt is superior for all pediatric patients with HLHS.”

These pediatric patients later undergo a second surgery at four to six months of age; and a third procedure, known as the Fontan procedure, at 18 to 36 months. Specialists are trying to ascertain answers to these outstanding questions: Which patients are suitable candidates for Fontan? What are their outcomes at the time of Fontan? What are their survival rates and ventricular function after the Fontan?

To answer these questions, the SVR II trial, an ongoing PHN-sponsored study, will follow the initial study patients out to six years of age, and discussions are in the works for an SVR III trial, which would follow these children out to pre-adolescent years, Gaynor says.

Long-term patient management

For the past 12 years, Gaynor has led the NeuroCardiac Research Group at CHOP, which seeks to determine the causes of developmental delays in children with heart disease and works on ways to reduce risks. Recently, Gil Wernovsky, MD, associate chief of the pediatric cardiology division at CHOP, launched a multidisciplinary, long-term follow-up program to assess congenital heart patients for neurodevelopmental complications, learning disabilities and behavioral concerns, such as ADHD. In the NeuroCardiac Care Program, children and their families are evaluated by a pediatric cardiologist, pediatric neurologist, developmental pediatrician, occupational and physical therapists, a speech and language pathologist, a dietician and a social worker—all during one outpatient visit. “Bringing many disciplines to the patients during one visit was initially logistically challenging, but has provided excellent service to the family,” says Wernovsky.

“Children with single ventricle defects have a significant incidence of neurodevelopmental disabilities related to the complexities of their heart disease, multiple surgical procedures and long hospitalizations. In addition to the neurodevelopmental concerns, there are emerging questions about the longer-term effects of the Fontan operation, which include both cardiac and non-cardiac problems,” says Wernovsky.

“As we have more operative survivors, there is a growing population who has never before lived to this age. We have much more to learn and understand to provide a normal quality and duration of life for these patients,” says Rychik. “The Fontan surgery is not a cure because it does not normalize the circulation, nor replace the missing pump chamber. Instead, it only mimics the normal circulation. In the absence of a pumping chamber, there are a number of developmental consequences to various organ systems.”

To evaluate children with single ventricle defects who have undergone operations including the Fontan procedure, Rychik and his colleagues have developed a Single Ventricle Care and Research Program—a “survivorship” program—to follow patients into their teens. The team includes cardiologists, nurses, cardiothoracic surgeons, gastroenterologists, hematologists and radiologists.

The multidisciplinary teams at CHOP are an example of how utilizing expertise from across the healthcare spectrum will not only help the present patient population, but will ensure that future generations of children with single ventricle defects will have a much better chance of living less complicated lives.