Spotting heart defect before birth improves babies' survival

March 04, 2001

DALLAS, March 6 - In a study of infants with a serious heart defect, babies diagnosed before birth - using a standard prenatal ultrasound - were more likely to survive the initial surgery to correct the defect, while only two-thirds of the babies diagnosed after birth survived. The study appears in today's Circulation: Journal of the American Heart Association.

"This is the first study to demonstrate that patients who are diagnosed prenatally with hypoplastic left heart syndrome (HLHS) have improved survival after the first-stage of surgery compared to those diagnosed after birth," says Wayne Tworetzky, M.D., the study's lead investigator and a clinical instructor in the department of cardiology at Boston Children's Hospital. The study was performed at the University of San Francisco.

Tworetzky says previous studies have not shown a significant benefit of prenatal diagnosis of HLHS. However, those studies were smaller and may not reflect recent medical advances in managing infants with this defect.

In HLHS, the left side of the heart - the heart's main pumping chamber - is underdeveloped and unable to support blood circulation after birth. Without treatment, the defect is usually fatal within the first several days of life. Treatment involves a series of surgeries. "Prenatal diagnosis has clear advantages," says Tworetzky. "It affords time for physicians both to counsel parents and to optimize early treatment, which allows the infant to be in the best condition for surgery."

He says that without the benefit of prenatal diagnosis, many babies with HLHS are born in a facility that is not equipped to care for them. "The delay in diagnosis may lead to the infant going into shock or suffering multiple organ damage among other complications - all of which limit the success of the initial surgery."

On the other hand, parents who have received prenatal diagnosis of HLHS and choose to have their infant undergo surgery can plan for their baby to be delivered at a medical center that is prepared to treat the condition.

"HLHS is an important congenital cardiac defect to study because the normal changes that occur in the newborn infant's circulatory system shortly after birth are not well tolerated by these infants," says Tworetzky. "The first operation is the most difficult and carries the highest risk of death."

Researchers compared the impact of prenatal and postnatal diagnosis on the preoperative health of infants with HLHS and reviewed the outcome of the crucial first stage of surgery. From July 1992 to March 1999, 88 infants were diagnosed with HLHS at the university - 33 prenatally and 55 postnatally.

After patients with HLHS are born, treatment includes medication and at least three stages of surgery. The first surgery is performed in the first week of life and involves reconstructing the aortic arch (the main blood vessel supplying blood to the body) and inserting a tube that connects the aorta to the pulmonary artery, which supplies blood to the lungs. The right ventricle assumes the role of the dominant pumping chamber, supplying blood to both the body and lungs. The second and third surgeries are performed at around 6 months and 18-36 months of age respectively.

At diagnosis, whether pre- or postnatally, parents in the study were counseled by a pediatric cardiologist and a cardiac surgeon. In 60 percent of the cases, parents elected to have the first surgery. While overall survival from surgery to hospital discharge was 75 percent, all of the babies who were diagnosed prenatally survived to discharge.

Babies who were diagnosed with HLHS after birth were generally sicker before going into surgery, and had poorer outcomes after surgery. About 66 percent of the infants diagnosed after birth survived the surgery.

Among the 52 infants who underwent surgery, those diagnosed prenatally had a significantly lower incidence of preoperative acidosis - a high lactic-acid level in the blood that occurs when there is insufficient blood supply to essential organs. These babies also had lower rates of ventricular dysfunction and were significantly less likely to need medications for resuscitation before the operation. When other factors were accounted for, only postnatal diagnosis remained significantly associated with early death.

"Our study suggests that prenatal diagnosis has the potential to improve surgical outcomes, possibly by means of ensuring the infant is in the best possible health prior to the operation," says Tworetzky.

Although HLHS is one of the most common cardiac defects found prenatally, Tworetzky adds that it is still more common for patients to be diagnosed after birth. Most of the patients who were diagnosed after birth in this study did undergo routine prenatal ultrasound screening. There are no known risk factors or genetic causes for HLHS; however, research is underway to investigate possible genetic links. Tworetzky and his team will continue to follow the patients from their study, gathering information on the infants' medium- and long-term outcomes.
Co-authors include Doff B. McElhinney, M.D.; V. Mohan Reddy, M.D.; Michael M. Brook, M.D.; Frank L. Hanley, M.D.; and Norman H. Silverman, M.D.

CONTACT: For journal copies only, please call: (214) 706-1396

American Heart Association

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