More than 90 percent of major structural heart defects can be detected in a fetus using ultrasound screening, says UCSF researcher
Lisa Hornberger, MD.
But sonographers, obstetricians, and radiologists currently doing routine prenatal screening find less than 20 or 25 percent of all heart defects.
"That means that basic fetal ultrasound screening is not sufficient," Hornberger says.
"One percent of babies have heart defects, and 20 to 30 percent of those are serious. That means we are missing them at the screening ultrasound currently performed on most pregnant women."
Hornberger and her colleagues are working with UCSF's physicans from many departments to improve ultrasound screening for fetal heart defects. That goal has gained momentum since the passage last summer of a new California law requiring such improvements in training for those who perform prenatal ultrasound screening.
Hornberger brings to UCSF her experience from the Hospital for Sick Children in Toronto. There she helped raise prenatal detection rates of major cardiac defects to 45 percent from an original 6 to 12 percent. For the detection of four-chamber view pathology, in particular hypoplastic left heart syndrome, detection rate climbed to about 80 percent.
"The ability to detect most major structural heart defects is fantastic because we know that prenatal detection improves perinatal and neonatal outcome. It's obviously critical for preparing families who are going to have an affected baby," Hornberger says.
"Being able to screen and eliminate the possibility of pathology is also important for families at risk for having a baby with a heart defect. It provides reassurance." With the right training and the proper technology, Hornberger and her colleagues are able to teach practitioners how to screen fetuses at 16 to 20 weeks.
Finding Defects in Even Younger Fetuses
Hornberger is also working with UCSF's fetal surgery team to detect cardiac defects in the fetus as early as 10 to 14 weeks, which she has been involved in since 1992. At this early gestational age, obstetricians and radiologists may look for nuchal, or "at the neck," thickening, caused by an abnormal accumulation of water.
"We know now that nuchal thickening is associated with cardiac defects in the absence of chromosomal defects," Hornberger says. Nuchal thickening with chromosomal defects can be an indicator of Down's syndrome.
Early detection becomes increasingly important as physicians refine methods to treat these disorders while the fetus is still in the womb. Certain types of cardiac defects, for example, may be repaired through interventional catheterization, Hornberger says.
"There are obvious benefits to treating a fetus for certain congenital conditions rather than waiting until after a baby is born," Hornberger says. "Many cardiac disorders are progressive, and evolve beyond the embryonic period. Early recognition and timely intervention may prevent some of the more severe secondary abnormalities that evolve as a consequence of a simple lesion. This secondary pathology may lead to the loss of the fetus or newborn, or a worse long-term prognosis after birth."
Operating on a fetus also offers another benefit: In the womb, a fetus is already hooked up to an efficient life-support system. Circulating hormones and peptides also promote rapid healing where incisions are made.
UCSF has long been a pioneer in
fetal surgery, so it is natural that Hornberger's research on fetal heart defects and their detection would connect with the work of UCSF fetal surgeons
Michael Harrison and
Diana Farmer.
In addition to her other work at UCSF, Hornberger and her colleagues are planning a fetal intervention on critical narrowing of the blood vessels leading to or from the heart. If left untreated while in the womb, these narrow points, called stenoses, can damage the heart in ways that can't easily be corrected if the physicans wait until after birth to fix them.
"If we can detect it and get in there early enough there is potential for preventing the progression of these serious defects," Hornberger says.
Source: Christopher Vaughan
