Looking for a heart attack test

Doctors across the nation and at Penn are searching for new ways to test patients' heart attack risk. Emergency rooms strive for both accuracy and efficiency when treating patients with chest pain. But figuring out which patients need expensive hospitalization because of the risk of a heart attack is no easy task. Nationwide, 2 to 5 percent of people sent home by emergency rooms after reporting chest pain have heart attacks. On the other hand, 70 percent of the patients reporting such pains to Penn doctors are at no risk of a heart attack -- and doctors have no way of knowing which group is which. The distinction is an important one. About 500,000 Americans die of heart attacks each year, according to the American Heart Association. Statistics such as these have doctors at the Hospital of the University of Pennsylvania and around the country busy researching new ways of figuring out which patients to treat for a possible heart attack and which to send home. Currently, most hospitals make determinations based on the patient's medical history and an electrocardiogram, which measures the heart's electronic activity. And most hospitals, including HUP, tend to err on the side of caution, often hospitalizing patients reporting chest pains who are not actually suffering heart attacks. "We admit a boatload of patients who turn out to have no significant disease," said Judd Hollander, an Emergency Medicine professor. One researcher looking into more accurate ways to diagnose heart attacks is the University's Emile Mohler, a Medicine professor who has just published a research paper about one such new method. His research focuses on a heart attack indicator called troponin-T, a protein released by the body when the cardiac muscle is damaged. It is one of several similar markers which scientists are looking at to help determine heart attack risk. Mohler's study showed that the test for troponin-T, in combination with an echocardiogram -- an image created by bouncing sound waves off the heart -- predicted the occurrence of a heart attack with 90 percent accuracy. Doctors at Temple University, where troponin-T tests are being gradually phased in, agreed that the test represents an improvement over existing methods. "Troponin-T is more accurate than standard measures and appears in the blood more rapidly," said David Wiener, a Medicine professor at Temple University Hospital in North Philadelphia. However, troponin-T can also be produced by other injured muscles, making it possible that a positive test may not necessarily signify cardiac damage. Troponin-I, a related protein, is only released by the heart, making it a better indicator, Hollander said. A test for troponin-I is already available. The HUP emergency room plans to begin using a troponin-I test by the end of the year. But Alan Forstater, a surgery professor at Jefferson Medical College in Philadelphia, remains skeptical of both troponin tests. "It really doesn't tell us much earlier than the standardized procedure whether or not a patient has had a heart attack," he said. One test that does produce immediate results is for a chemical called myoglobin. But myoglobin is produced by all injured muscles, causing difficulties similar to those of troponin-T. Researchers have tried pairing the myoglobin test with another test for carbonic anhydrates-3. The anhydrates are only released by skeletal muscles, allowing doctors to compare the two levels and determine if the myoglobin is being produced by non-skeletal cardiac muscles. That test is not yet commercially available. Researchers are also experimenting with tests triggered by markers of platelet adhesion -- the process of clotting which precedes a heart attack -- which test positive even before the heart attack actually begins. But none of these tests tells doctors if a patient's heart is structurally at risk for heart attacks, which makes imaging technology indispensable. The echocardiogram that Mohler's study used can only be interpreted by an expert. This is particularly problematic at night, when fewer experienced doctors are on hand. That problem can be remedied. Doctors at Indiana University in Indianapolis have already developed digital imaging systems which allow them to send images to experts in remote locations at all hours of the day. HUP is currently working with Eastman Kodak to produce a similar digital system. Another system, used by doctors at the Medical College of Virginia in Richmond, is called a setamibi. It uses radioactive traces injected into the body to check the flow of blood through the heart. Although the method is promising, the need to keep radioactive material on hand creates complications stemming from the high costs and danger of the materials. "Unless you do a lot of these [tests], it's hard," said Hollander. While doctors wait for a perfect technology to arrive, they've devised temporary measures to hold down the high hospitalization rates. One such method employed at Thomas Jefferson University Hospital utilizes a holding area for patients complaining of chest pain. This intermediate stage allows doctors to evaluate patients and reach a more accurate determination of the risk of heart attack without actually admitting them, Forstater said.