What we know about congenital heart disease:
- Definition: The term congenital heart disease (CHD) encompasses structural heart problems, such as abnormal heart valves or holes in the heart, and functional problems, such as disorders of the heart muscle (hypertrophic or dilated cardiomyopathy), and disorders of heart rhythm (e.g., long QT syndrome). Some CHD may go undetected until adulthood. In adults, CHD often is diagnosed after heart failure develops or an arrhythmia causes sudden cardiac death.
- Frequency: CHD is the most common birth defect. It comprises over 30 types of defects, ranging from mild to severe. Some forms of CHD resolve without therapy, others are fully correctible, and others are life-threatening either early or later in life. Nearly 3 children out of every thousand live births have severe CHD requiring early surgery, while another 13/1000 require surgery or catheter-based intervention later in childhood.
- Causes: Both genetic and environmental factors may cause or contribute to cardiac malformations.
- Survival: The mortality rate has decreased nearly 40 percent in the last 18 years; in 2005, CHD was responsible for about 3600 deaths. Today, more adults than children are living with CHD because medical advances have enabled more infants with heart defects to survive to adulthood. The number of adults living with CHD continues to grow, and the number of adults with CHD admitted to the hospital each year has doubled over the past decade. Research and medical care focus on both the duration and the quality of life for individuals with CHD.
- Outcome: The outlook for patients depends on multiple factors, including the nature of the lesion; genetic causes and associations; early recognition, referral and diagnosis; the skill of the surgical team and the quality of perioperative care; medications; and interventional catheterization. Most of the drugs and devices used in pediatric patients have never been tested in children and are approved only for use in adults.
What we need to learn to make progress:
- Developmental biology: More research is needed to improve understanding of the environmental, genetic, cellular, and molecular components, and pathways that cause hearts to form normally and abnormally. Research also is needed to determine how genetic and environmental factors interact to support normal or cause abnormal development.
- Tissue engineering: One day, researchers may be able to use tissue engineering to grow new heart valves or pumping chambers.
- Pediatric devices: Development of pediatric devices, such as mechanical pumps that can support failing hearts, requires fundamental research – devices cannot simply be scaled down to fit children. Industry does not support much work in this area because the pediatric market is very limited and development costs are high, with substantial economic and liability risk. More research is needed to develop devices tailored to pediatric heart disease patients.
- Early diagnosis: Fetal ultrasound can identify affected children, greatly facilitating early diagnosis and treatment, and protecting the brain. More research is needed to optimize the use of this technology, including determining whom to test, and at what time in development.
- Practice variation: Congenital heart defects vary and treatment can include surgery, catheter-based intervention, and medication, making standardizing therapeutic approaches difficult. Analysis of the role of practice variation on outcomes may identify more efficient, effective, and easier-to-implement strategies for treating CHD.
- Protecting the brain: Open-heart surgery takes a toll on the brain. Research to enhance neuroprotection may improve outcomes for patients with CHD.
- Heart transplantation: Sometimes the best treatment strategy for CHD is to replace the malformed heart. More work is needed to increase the donor pool, especially for infant hearts, and to improve organ preservation
- Comparative effectiveness research: Clinical trials are needed to address a variety of questions ranging from optimal control of bleeding in the perioperative period to optimal nutritional support.
- Registries: Systematic longitudinal data collection beginning in utero could help to answer many questions about risk and outcomes, including recurrence risk of CHD in families. Such registries should be linked to biological samples so that genetic information can be linked to clinical course and outcome.
National Heart, Lung, and Blood Institute (NHLBI) current CHD research and related resources:
The NHLBI provides scientific leadership for CHD research, and currently supports several large Institute-initiated programs and a diverse investigator-initiated grant portfolio. As noted in the Congenital Heart Futures Act, NHLBI strategic plans have emphasized the importance of research for children and adults living with CHD. Highlights of current activities and potential future research follow:
- Grant Portfolio. The NHLBI supports a robust portfolio of investigator-initiated research grants on cardiac development.
- Pediatric Heart Network. Since 2001, the NHLBI has supported the Pediatric Heart Network (PHN), a multi-center collaborative group that conducts clinical studies in individuals with CHD. The large number of different types of defects and the complex medical, interventional, and surgical care that many patients require make conducting clinical CHD research difficult.
- The PHN’s first study, the Fontan study, is evaluating and following older children and young adults who have undergone the staged surgical approach culminating in the Fontan procedure for single ventricle physiology. The PHN recently completed two landmark trials in infants born with only a single functional ventricle. In one trial, two surgical procedures were compared in over 550 infants. In the other, a medical therapy commonly used in adults was evaluated in over 200 infants. Results will be published soon. Since 2001, the PHN has launched 9 studies.
- Bench to Bassinet Program. In 2009, the NHLBI began its “Bench to Bassinet” program, which combines two collaborative consortia, the Cardiovascular Development Consortium and the Pediatric Cardiac Genomics Consortium, that align with the PHN. The program, currently in its planning phase, is laying the foundation for high-throughput, nimble, state-of-the art approaches to understanding the genetic causes of CHD and the genetic influences on outcome.
- The Bench to Bassinet program will offer an unprecedented opportunity to gain new information to guide the care of children and adults with CHD. For example, several different genetic mutations can cause the CHD known as tetralogy of Fallot. Although patients who undergo surgery to repair tetralogy of Fallot often have different long-term outcomes, the reason for the different outcomes is unknown. New information about genetic mutations related to tetralogy of Fallot or other conditions may allow for personalized treatment of adult congenital heart disease (ACHD) by using genetic information to determine whether a particular patient could benefit from a pacemaker, early pulmonary valve replacement, or certain types of medical therapy.
- Health Education and Access Research Trial in ACHD. The NHLBI funds the grant, “Health Education and Access Research Trial in Adult Congenital Heart Disease,” which is a partnership between the Adult Congenital Heart Association and the Alliance of Adult Research in Congenital Cardiology. The multi-center study seeks to improve care delivery and long-term outcomes for adults with CHD and to improve subsequent care and outcomes study designs.
- Obesity and Other Risk Factors in Children with CHD. The NHLBI held a Working Group on Obesity and Other Cardiovascular Risk Factors in Children with Congenital Heart Disease in May 2009. The relationship between childhood obesity and subsequent cardiovascular risk has been well-described. Pediatric cardiologists have found that children born with CHD are now becoming overweight and obese at rates similar to those of the general pediatric population. This raises the specter of adding all of the risk implicit in obesity to a group of children already at increased risk of adverse cardiovascular outcomes. Recommendations from the working group focused on combating conventional cardiovascular risk factors in individuals with CHD whose underlying condition may put them at increased risk.
- Children and Clinical Studies. Research on children and young adults entails unique challenges. A key component of successful pediatric research is educating the public about participating in such research. To that end, the NHLBI developed the award-winning “Children and Clinical Studies” website as a resource for families and health care providers. The website, in Spanish and English and accessible for a diverse population, can be found at www.ChildrenAndClinicalStudies.nhlbi.nih.gov. This effort supports a key priority, reinvigorating the biomedical research enterprise by informing the public about the importance of research. of the NIH Director, Dr. Francis Collins.
Potential Future Research:
- Congenital Heart Disease Registry. The NHLBI currently participates in the Congenital Heart Disease Public Health Consortium, led by the CDC. The Institute will continue to work with the CDC and the Consortium to develop a CHD registry. Longitudinal studies such as the Framingham Heart Study indicate that this approach offers enormous scientific and therapeutic potential, particularly when the epidemiological data are linked to genetic and other biological information.
- Protecting the Brain. Many individuals with congenital heart disease have neurocognitive impairment and depression. Now that survival is virtually assured, focus has shifted to the quality of life. Although NHLBI programs currently support some research in this area, far more research is needed to identify preventive and therapeutic strategies.
- Comparative Effectiveness Research and Practice Variation. Although the PHN conducts clinical trials, a number of clinical questions, ranging from optimal control of bleeding in the perioperative period to optimal cardiac rehabilitation strategies to optimal medical and surgical therapy for the many types of CHD, remain to be answered. Further, the variation in congenital heart defects and the fact that treatment often includes a combination of surgery, catheter-based intervention, and medication, means that standardizing therapeutic approaches is likely to be difficult. Analysis of the role of practice variation on outcomes may not only provide “best practices”, but also prove cost-saving in the long run.
- Tissue Engineering. The ability to grow a new heart valve, or have bioactive conduits that grow with a patient, could potentially eliminate the need for repeated surgical procedures to replace faulty valves and outgrown conduits. The NHLBI supports research in this area, but a focused effort could accelerate progress.
- FDA, CDC, AHRQ, HRSA
- Industry – new drug and device development especially for pediatrics
- Health care systems to enhance implementation of current knowledge and advancement of future research
The NHLBI has awarded grants in congenital heart disease since its first grant cycle in 1949, when it was the National Heart Institute. The Institute’s current programs are a testament to the importance of this research. However, despite the progress made in understanding and treating CHD, more work is needed to determine the causes of congenital heart disease, the best ways to treat it at all ages, and how optimal long-term outcomes can be ensured.