Cardiologists go beyond diagnostics to correct problems without surgery

Pediatric echocardiographer Norman Silverman, M.D., developed a novel technology that allows surgeons and cardiologists to see a live picture of all four chambers of a child's heart.

WINTER 2002 - The focus of the field of pediatric cardiology traditionally has been the diagnosis and characterization of heart problems in children. "What we do encompasses everything but surgery," says Daniel Bernstein, M.D., chief of the pediatric cardiology program and associate director of the Children's Heart Center. "But the field of cardiology has evolved considerably in the last 20 years, producing noninvasive imaging tools such as 3-D reconstructions of the heart, and even non-surgical interventions to repair heart defects without opening the chest," adds Bernstein, who has helped build an exceptional pediatric cardiology program at Packard.

Heart problems are the leading cause of death among all birth defects. Stanford Medical Center long has been a leader in cardiology research and heart surgery, making it a natural place for the development of an excellent pediatric cardiology program. Starting in the 1960s, Norman Shumway, M.D., pioneered adult and pediatric heart transplantation at Stanford. Cardiologists at Packard Children's Hospital carry on that tradition and, combining laboratory and bedside research, are making strides in understanding the basic mechanisms and treatment of heart failure in children.

Some of Packard's greatest successes in cardiology have been in developing new techniques for controlling life-threatening cardiac arrhythmias, in which the heart beats irregularly or too rapidly. Other successes have come in the area of new medications. "We are embarking on a new era in which there are new drugs and techniques that preclude or delay transplantation in many cases," says Bernstein.

A View of the Heart

One critical part of the Packard cardiology program is the echocardiography lab. Echocardiography uses the "echo" of high frequency sound waves -- ultrasound -- to make structures of the heart visible on a computer screen. Such images can be used both to diagnose heart problems to determine if surgery is necessary, and in the operating room to help guide physicians during complex operations. Echocardiography is also used to assist cardiologists during minimally invasive diagnostic procedures.

In years past, when diagnosing heart problems in children, cardiologists were limited to interpreting the meaning of a wavy line on an electrocardiogram or using invasive procedures. Standard practice now is to make a diagnosis using a non-invasive, twodimensional, ultrasound view of the heart, so that doctors can see a live-motion picture of all four chambers in action as the valves open and close.

Norman Silverman, M.D., the renowned physician who developed the technology for this four-chamber view of the heart, recently was recruited to the Children's Heart Center from the University of California, San Francisco. In addition to the fourchamber view technology, Silverman also has made many other important contributions to the field, including the development of special ultrasound probes that fit down a child's esophagus. These probes offer finely detailed pictures of the internal structure of the heart during surgical procedures.

Silverman is now using ultrasound to research fetal physiology and development, knowledge that will be key as physicians try to correct cardiovascular problems earlier in a child's development, at a time when problems may be more readily repairable. "We now are to the point that we can operate on tumors around the heart in a fetus that is still in the womb," Silverman says.

Just as Doppler radar allows meteorologists to gauge wind speeds, Doppler echocardiography allows physicians to measure the speed of blood flow. This is an invaluable tool, letting doctors see "jets" of blood as they squirt through heart valves or abnormal holes in the heart. Knowing the velocity of blood flow, they also can infer blood pressure in various parts of the cardiovascular system and determine the severity of blocked heart valves or other life-threatening abnormalities.

"We help surgeons every day," Silverman says. "It used to be that kids would go from surgery to intensive care, and then we would wait to see if the child's heart was still sick. If so, we would take them back to surgery. Now when the surgeons finish we can use ultrasound right there in the operating room to see how the repair is working, and whether there is a residual problem that still needs to be fixed."

Repairing Heart Defects Without Surgery

Complementing the echocardiography lab is the catheterization lab. Before echocardiography, catheterization was the only way to get an accurate view of the inner workings of the heart before surgery. During catheterization, the patient is sedated, and a thin tube (catheter) is inserted into an artery or vein in the leg and threaded up to the heart. Doctors watch the progress of the catheter using a fluoroscope. Dyes that are opaque to x-rays then can be squirted into the bloodstream, making the flow of blood through the heart and lungs visible.

Catheterization still provides details of a child's blood flow not obvious on echocardiograms, and also can give precise information about blood pressure and oxygenation in particular regions of the cardiovascular system. Increasingly, however, catheters are being used to make repairs to the heart or blood vessels in a non-invasive, non-traumatic way.

While at Children's Hospital Boston, Stanton Perry, M.D., used a catheter inserted through a mother's womb to correct a deadly heart defect in a 23-week-old fetus. Perry is now an interventional cardiologist at Packard Children's Hospital.

Stanton Perry, M.D., is one of the foremost physician- scientists in this field. Recruited to Packard this year from Children's Hospital Boston, Perry has found innovative ways of repairing critical heart defects in children, infants, and even fetuses. "We are really looking to do new and different things, developing techniques and devices that are not being done anywhere else," Perry says.

One device that Perry has worked on is a spoolshaped wire cage that can be inserted with the catheter in collapsed form, and then expanded in a hole in the heart to plug it. Cardiac tissue eventually grows over the device, making it a permanent part of the heart. This device has replaced open-heart surgery for repair of many cardiac defects.

Another important area of research focuses on using catheters to correct the course of fetal heart development so that extensive repairs do not have to be made after birth. Perry worked on a recent case in which a heart valve in a 23-week-old fetus displayed signs of marked narrowing, or stenosis. A severe stenosis of this valve can lead to insufficient growth, or hypoplasia, of the heart during development. The result is often a life-threatening problem that can be corrected only through extensive surgery or heart transplantation. Early correction, when the heart is still developing, can prevent this hypoplasia. In this case the fetus and the mom were put to sleep. Perry inserted a catheter and expanded the blocked valve. Months later, the baby was born with a normal heart.

Such advances in pediatric cardiology have made possible cures that could only be dreamt of before, and allowed the correction of many children's heart problems without the need for surgery.

"In some ways cardiology has become more like surgery, while surgery -- with minimally invasive technologies -- has become more like cardiology," Bernstein says. "Collaboration between cardiologists and surgeons to provide the safest, most effective treatment for our patients is what the Children's Heart Center is all about."