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Richard Bianco, director of experimental surgery in the University's Experimental Surgical Services (ESS) laboratories, holds an artificial heart valve made from a pig heart valve. ESS tests 90 percent of heart valves destined for human patients.
Holding up under pressure
The University is a major center for pre-testing heart valves before they are approved for human use
By Deane Morrison
June 23, 2006
As he lowers a new valve into a heart, Matthew Lahti explains the delicate procedure to New Hampshire businessman Bill Matson. "You must get the valve low enough so it doesn't block the openings of the coronary arteries," says Lahti, a staff member at the University's Experimental Surgery Services (ESS) laboratories. The valve fits at the junction of the heart and the aorta, the body's main artery. The first branches of the aorta are the coronary arteries, and a valve placed too high will choke them off. Once the valve is in place, Lahti invites Matson to suture it to the heart wall. Matson has never sutured anything in his life, but he gamely wields the needle. Not to worry, though; the men are working on an isolated pig heart. It is June 16, 2006, exactly a year since a valve similar to this one was sewn into Matson's own heart. That valve had been tested in nonhuman animals by staff at ESS, where Matson is now visiting. Such testing is required by the Food and Drug Administration before valves can be approved for clinical trials. ESS performs preclinical testing on 90 percent of all heart valves. ESS is a natural place for this kind of work. Besides its proximity to several companies that manufacture medical devices, the University got a leg up more than 50 years ago, when Drs. F. John Lewis and Richard Varco, with Dr. Walton Lillehei assisting, performed the world's first open-heart surgery. In 1955, Lillehei and Richard de Wall invented a bubble oxygenator that made heart surgery safe and practical. Lillehei also helped develop the external battery-operated pacemaker. Another reason for the University's prominence in this field is because, while it performs tests on behalf of private companies (as well as faculty researchers), it has no financial stake in the outcome of the tests. The University follows FDA guidelines in carrying out the tests, which lends uniformity, as well as high standards and objectivity, to the procedures. In the case of Matson's valve, everything has gone very well. "They had me walking two days after surgery," he says. "Four days after surgery, I could walk upstairs, and they sent me home. After five days, I went back to work." Matson was visiting the University after spending the first five months of the year biking here from San Francisco. "Our lab puts valves in sheep, sometimes dogs or pigs," says lab manager Lynn Hartman. "We follow them usually for five months or more. We evaluate the heart function without surgery. We do several echocardiograms to determine how much blood the heart is pumping out and how it's functioning. Near the end, we do angiography to see the valve in motion." After the animal is euthanized, ESS performs a necropsy (autopsy of a nonhuman animal) to check the heart and the valve for gross or microscopic damage.
"We've tested most of the heart valves available in humans. Most that we test don't pass right away," says Bianco."There are two types of heart valves," explains Richard Bianco, director of experimental surgery at ESS. "There are tissue valves, made from tissue like the pericardium (the sac surrounding the heart) of a cow or from actual pig heart valves, and there are mechanical valves. We've tested most of the heart valves available in humans. Most that we test don't pass right away." Today millions of people worldwide use heart valves, Bianco says. An impetus for early research on valve replacement was the prevalence of rheumatic fever, an infection that destroys the heart's mitral valve. Situated between the left auricle and ventricle, the mitral valve takes the most punishment of any valve. That's because the left ventricle's muscles, which pump blood to all of the body except the lungs, contract with a mighty force and generate tremendous pressure in the chamber. The mitral valve's job is to withstand the force of contraction and keep blood from squirting back into the left auricle. Rheumatic fever is now under control, says Bianco, but the science of valve replacement still has hurdles to clear. For example, Matson's valve--an aortic valve, which keeps blood from draining out of the aorta and back into the left ventricle--is a mechanical valve that may not last the 40-plus years it is designed to. Other items on the researchers' wish list are mechanical valves that require no blood thinners, as they are wont to now; tissue valves that last longer; and, ideally, valves that can be grown from a patient's own tissues. Plenty of research remains to be done, and the ESS is in the thick of it. "Besides testing heart valves and other medical devices, the ESS performs basic scientific research on new surgical techniques, especially those that are minimally invasive, and trains residents and practicing surgeons in new procedures," says Bianco. "We do more than 1,000 procedures every year. We're by far the biggest testing lab at a public university. Private places like Brown University and the Texas Heart Institute also have labs, and we keep in contact." ESS also brings in undergraduate students to learn the ropes. "We have a mix of staff and students here," says Laura Sorcic, an undergraduate in the College of Biological Sciences. "There are eight undergrads working part time, about 20 hours a week. We do cleaning, prep work for surgery, and care for the sheep." On the day of Matson's visit, Tami Williams, a surgeon from southeast Missouri, was operating on a pig down the hall from the room where Matson had his lesson in surgery. Williams was training on the da Vinci surgical system, a $1.5 million computerized apparatus that uses robotic arms to wield instruments. Surgeons, who direct the arms from a control panel, get a binocular view of the surgical site on the computer screen. "I'm practicing ligation, which means tying off an organ to get it out of the way," says Williams. She heartily endorses the da Vinci system, which, according to Bianco, is becoming the norm for surgery around the country. "It makes a lot of difference being able to manipulate the instruments by reproducing wrist movements," she says. The combination of research, testing, and training puts the ESS squarely at the forefront of surgical progress in the new century. And its effects are palpable. "I wanted to come here on the first anniversary of my valve replacement to see the lab where the research happened," Matson said in a press release before his visit. "The work done here changes lives."