PET MPI provides a more accurate "picture" of coronary obstruction

Aug 17 2007

Physicians need to know how badly heart vessels are blocked before they can decide how to treat patients at risk of having a heart attack.

One standard approach to "imaging" suspected blockages involves injecting a radioactive substance with a very short half-life into the blood stream. The patient then undergoes an exercise stress test, and the radioactive material is tracked as it travels through the cardiovascular system, identifying narrowing or blockage.

That process is called single photon emission computed tomography, or SPECT.

A study published in the July 2007 issue the Journal of Nuclear Medicine shows that a newer imaging method called positron emission tomography myocardial perfusion imaging, or PET MPI, provides a more accurate "picture" of coronary obstruction, costs 30 percent less, reduces the need for follow-up invasive procedures by 50 percent and produces excellent clinical outcomes.

Michael E. Merhige, M.D., clinical associate professor of nuclear medicine in the University at Buffalo School of Medicine and Biomedical Sciences, is first author on the study.

"Our evidence has shown that invasive procedures such as coronary arteriography [inserting a cardiac catheter into an artery in the upper arm or thigh, threading it through the vessel and injecting a contrast medium directly into the heart], bypass surgery and stent placement are overused in the U.S.," said Merhige.

"Using these procedures when non-invasive approaches work equally well, if not better, contributes to unnecessary health-care expenses without improved patient outcomes."

Merhige is medical director of The Heart Center of Niagara, located in the Niagara Falls Memorial Medical Center, where he carried out his research.

The study analyzed the frequency of diagnostic arteriography, revascularization, costs and one-year clinical outcomes in 2,159 patients assessed with PET MPI. These results were compared with outcome data from two control groups totaling nearly 6,000 patients who were assessed with SPECT, matched to the PET group by pre-test likelihood of coronary artery disease.

The actual costs of the two procedures were similar, Merhige said, but the accuracy of PET MPI eliminated the need for additional coronary artery bypass grafting procedures in more than half of the participants. SPECT MPI also is less accurate that PET MPI in women and overweight patients, he noted.

"This study supports the idea that the future of cardiology lies in non-invasive imaging, combined with aggressive use of cholesterol-lowering drugs and lifestyle changes, such as better nutrition, regular exercise and smoking cessation," he said.

Also contributing to the study were cardiologists William J. Breen, M.D., Brian J. D'Arcy, M.D., and Anthony F. Perna, M.D., UB clinical instructor of medicine, and nurses Victoria Shelton and Teresa Houston.

The University at Buffalo is a premier research-intensive public university, the largest and most comprehensive campus in the State University of New York. The School of Medicine and Biomedical Sciences is one of five schools that constitute UB's Academic Health Center. UB's more than 27,000 students pursue their academic interests through more than 300 undergraduate, graduate and professional degree programs. Founded in 1846, the University at Buffalo is a member of the Association of American Universities.