Researchers Use Pet Scans To Reduce Need For Heart Transplants
NEW YORK, NY, April 15, 1999 -- Does everyone on a heart transplant list truly need a transplant? Or might some be helped by other cardiac procedures? Responding to the shortage of donor hearts, cardiologists at the Columbia Presbyterian Center of the New York Presbyterian Hospital have successfully used positron emission tomography (PET) to identify those patients who can be helped by coronary artery bypass surgery rather than a transplant.
The results of their study were published in the April 15, 1999, issue of the American Journal of Cardiology, authored by Olakunle Akinboboye, M.D., Assistant Professor of Clinical Medicine at the Columbia University College of Physicians & Surgeons and Assistant Attending Physician of Medicine and colleagues at Columbia Presbyterian Center. The article concludes that routine cardiac diagnostic tests such as thallium exercise stress tests, can underestimate the amount of healthy heart muscle a patient has, missing those portions that are still alive but starved of blood and oxygen.
"We specifically looked for areas in the left ventricle where there is sluggish blood flow but good metabolism, an indicator of viable heart muscle," explains Steven R. Bergmann, M.D., Ph.D., who is the senior investigator of the study. Dr. Bergmann is also Director of Nuclear Cardiology at the Columbia Presbyterian Center and Professor of Medicine and Radiology at the Columbia University College of Physicians & Surgeons. "We've shown that once the PET scan identifies such areas, we can take these patients off the transplant evaluation list and treat them successfully with bypass surgery, thus saving the scarce donor hearts for patients who really need them."
The Columbia Presbyterian Center is the only facility in the metropolitan area to routinely use PET scanning in this manner. PET provides a more detailed picture of blood flow than thallium scanning. It also depicts the level of metabolic activity, which thallium scanning cannot.
As Dr. Bergmann explains, "You can think of damaged heart tissue as a brown lawn. Normally, you'd think that the brown means the lawn is dead. PET allows us to determine if there's still some life left in that brown. If there is, then bypass, rather than a transplant, is usually the way to go. And the bypass surgery is like turning on a garden hose that waters and renews the brown, turning it green."
The study evaluated the viability of cardiac myocardium, or heart muscle, in 33 patients with coronary artery disease who were referred to the Columbia Presbyterian Center for cardiac transplantation. Seventeen were found to have viable myocardium, which made them good candidates for bypass. Of these, 11 underwent bypass surgery, two refused the procedure, and four were ineligible because of other health considerations.
The postoperative outcomes of these 11 bypass patients were not significantly different from the average outcomes for all patients who underwent the procedure at the Columbia Presbyterian Center during the study period. Both groups were compared for duration of cardiopulmonary bypass, length of intensive care unit and total hospital stay, and in-hospital mortality. "The patients who underwent bypass surgery recovered relatively quickly, and their ejection fraction, which measures the heart's pumping power, improved significantly," notes Dr. Bergmann.
Specifically, the ejection fractions in 10 of the 11 patients increased from an average of 22 percent to 33 percent. Normal ejection fraction is 50 percent. In contrast, there was no improvement in ejection fraction in 7 patients in whom PET found no evidence of cardiac viability. (Their measurements were available after an average of six months of medical therapy.) In addition, none of the bypass patients experienced a heart attack or cardiac death during an average follow-up period of 12 months (range: 8-19 months).
Of the remaining 16, only five received transplants within one year. Among the other 11 patients, there were two cardiac deaths and one nonfatal heart attack within the same time period.
"Surgeons have been reluctant to operate on patients with poor ventricular function because of concerns that they may not tolerate bypass surgery very well. But our study shows that if they have enough viable myocardium, they will do well with the procedure," says Dr. Bergmann.
The researchers estimate that 30 to 50 percent of those referred for heart transplants can be successfully treated with bypass surgery. "Our study demonstrates very strongly that we can probably remove many people from the heart transplant list and offer them a less life-altering therapy. And then those who really need a donor heart will have a better chance of receiving one," notes Dr. Akinboboye.