Heart specialists team up to provide "hybrid" procedure for newborns
October 18, 2004
Two heart specialists at the University of Chicago have developed a new approach, called "hybrid surgery," for treatment of newborns with hypoplastic left heart syndrome (HLHS). Instead of a series of major operations that pose considerable risk, the hybrid approach combines non-surgical interventions with a less drastic operation. Although still being tested and refined, it appears to offer better results.
The University of Chicago is one of only two hospitals in the United States using hybrid surgery to treat HLHS.
"Initially," says Emile Bacha, M.D., director of pediatric cardiac surgery, "we were only doing hybrids on high-risk patients and using the standard Norwood method for the low-risk cases. But the hybrid technique has proved so successful that it has replaced the Norwood method for use with newborns at the University of Chicago Children's Hospital."
Children born with HLHS have a long list of cardiac abnormalities and would die within a week without treatment. In HLHS, neither the heart's main pumping chamber, the left ventricle, nor the body's primary blood vessel, the aorta, is properly formed. As a result, the heart is unable to pump blood effectively to the body.
Additional abnormalities in the mitral valve, which regulates flow from the left atrium into the left ventricle, and the aortic valve, which controls flow from the left ventricle into the aorta, complicate surgical treatment. Many of these infants also have an atrial septal defect -- a hole in the wall of the heart that separates the two atria.
In the past, infants born with HLHS had two options: a heart transplant or a complex series of operations to rebuild the heart in a way that provides stable blood flow to the body and the lungs but sustained by a one-ventricle heart.
Few hearts are available for transplantation in infants, so most HLHS patients are treated soon after birth with the difficult and risky Norwood operation. Those that survive undergo the Glenn operation, four to six months later, and the Fontan operation, performed once the child is 2 to 3 years old.
In newborns, especially those born prematurely, the risk of open-heart surgery is considerable. These tiny infants have very small hearts and cannot easily tolerate the periods of decreased blood pressure, cold, or the other manipulations required to perform the Norwood. Also, reliance on the heart-lung machine (bypass machine) and stopping the heart to operate can cause loss of oxygen to the brain leading to brain damage.
"We have the tools to fix many congenital heart problems using a catheter that would have required major surgery just a few years ago," said Ziyad M. Hijazi, M.D., section chief for pediatric cardiology at the University of Chicago Hospitals. "This is a novel way to combine those tools with smaller operative interventions. We now think we can get the same rewards with far fewer risks."
The traditional Norwood procedure has up to a 20 to 30 percent mortality rate, depending on various risk factors such as the size of the aorta (sometimes as narrow as 1mm), the degree of prematurity, the weight, the age, or the presence of an infection.
Hybrid surgery provides a "non-open-heart approach" that, although new and still being evaluated, appears to be safer and more effective. The hybrid procedure’s mortality rate over the last 12 months at the University of Chicago Children’s Hospital for treating comparable infants is 11 percent (9 performed with 1 death).
The hybrid approach does not require use of the heart-lung machine nor does it require stopping the infant's heart. This reduces the risk of neurological damage associated with the traditional approach.
Hybrids are performed not in an operating room but in a catheterization lab. The chest is opened briefly to gain access to the heart and the pulmonary arteries (vessels going from the heart to each lung). Through small openings, Bacha’s surgical team places restrictive bands around these vessels to narrow them, restricting blood flow to the lungs.
Next, Hijazi and Bacha work together to deploy a stent -- placed via a direct vessel puncture in the chest -- that keeps the ductus arteriosus open. This blood vessel, which normally closes soon after birth, connects the pulmonary arteries to the aorta. By keeping this vessel open, the stent allows blood pumped by the right side of the heart to flow into the aorta and out to the child’s small body. Using a chest puncture to place the stent preserves the groin vessels for future catheterizations.
This combination of less-invasive measures buys time, enables the child to survive without a massive operation soon after birth and allows the child to grow for several months, which makes the follow-up operations easier. By replacing the Norwood reconstructive procedure with this series of smaller interventions, the hybrid technique reduces the risks of brain damage associated with the bigger operation.
The second and third surgeries for HLHS -- known as the Glenn and the Fontan operations -- reroute blood returning to the heart directly to the lungs, where it exchanges carbon dioxide for oxygen. These are scheduled as before, but the Norwood, the major open-heart procedure with the greatest risk of serious side effects and death, has been removed from the sequence.
Other conditions treated jointly by the "hybrid" combination of cardiac surgeons and interventional cardiologists now include:
- Ventricular septal defects (VSD)
- Atrial septal defects (ASD)
- Pulmonary stenoses
- Valve replacements
Using techniques from both teams, doctors aim to reduce the total invasiveness of traditional surgeries.
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