NEW YORK, Sep 15 (Reuters Health) -- In heart patients with a common abnormality on their electrocardiogram (ECG), the results of an exercise treadmill test can help predict those at high risk for later heart attack or cardiac death, according to a report published in the September 15th issue of The Journal of the American Medical Association.
"Our data demonstrate that the Duke treadmill score is capable of predicting not only cardiac death but also total cardiac events" for patients with ST-T abnormalities, according to a team from the Mayo Clinic in Rochester, Minnesota, led by Dr. Jennifer M.F. Kwok.
Kwok and her colleagues followed a group of 939 patients whose resting ECGs showed abnormalities in the T-wave and the ST-segment, and compared them to a 'control' group of 1,466 patients with normal ECGs. All patients were being evaluated for cardiac disease because of chest pain or shortness of breath, and took the treadmill test after being injected with a radioisotope called thallium, which helps doctors to detect damaged areas of the heart on special scans.
Treadmill scores were classified as low risk, intermediate risk, and high risk based on a system called the Duke classification. Patients with ST-T abnormalities had significantly lower treadmill scores than those with normal ECGs: 45% scored in the low-risk group, 49% in the intermediate group, and 5% in the high-risk group. These patients also had a significantly worse 7-year outcome, indicated by increased risk of cardiac death, heart attack, and need for heart surgery.
For patients with ST-T abnormalities, there were significant differences among the three risk groups. Cardiac survival at 7 years was 97% in the low-risk group, 92% for the intermediate group, and 76% for the high-risk group. The other outcomes measured were also significantly different for the three risk groups. The patients with ST-T abnormalities in each risk group also had significantly worse outcomes than control patients in the same risk group.
"This study clearly demonstrates the value of an exercise ECG for risk-stratifying these patients," Kwok and her team concluded. They point out that almost half of the study group were classified as low risk, and thus would not require treatment such as surgery, while the much smaller group of high-risk patients would need early assessment for surgery.
