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Every year in the United States, some 35,000 babies are born with congenital heart defects: holes or narrowings in the wrong places, misshapen chambers and valves too stiff or too weak to open and close properly. One in three cases requires surgery, and most of these operations necessitate stopping the heart and using cardiopulmonary bypass, allowing surgeons to work on a still, bloodless heart. It's the best way to see and reach structures inside the heart, the surest way to avoid accidentally jabbing delicate spots and the only way to work on fast-moving parts, such as valves.
But it's still risky enough to worry Pedro del Nido, MD, chief of Cardiac Surgery at Children's Hospital Boston. The child's immune system may react to the cardiopulmonary bypass machine, causing rare but dangerous complications such as blood clotting and inflammation in different organs of the body. Although bypass techniques have become safer over the years, micro air bubbles may still enter through the open heart and travel to the brain, causing damage. And because the heart doesn't receive circulation during surgery, sometimes for lengthy periods during complex repairs, it may suffer damage and fail to beat properly once it's restarted.
For about a decade, Dr. del Nido, who repairs about 250 children's hearts a year, has been exploring ways to avoid stopping the heart during surgery. Currently, beating-heart repairs are limited to atrial septal defects (ASD) and a small number of the simplest ventricular septal defects (VSD). (The majority of septal defects in children can't be repaired on beating hearts because existing repair devices are too bulky for newborns and don't fit many types of holes.) During the procedure, cardiologists, guided by an X-ray and 2-D ultrasound imaging, pass a catheter from the groin blood vessels into the heart and place a metal plug in the hole. Rare complications, like bleeding, clotting, infection and tears of the heart muscle, still occur, and in some cases, the plug can get dislodged. In addition to these risks, surgeons lack many of the catheter-compatible tools and clear 3-D real-time imaging of the heart's inner structures to perform more complex repairs. // cont.
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