Two groups of patients do not benefit from a CTA scan to rule out coronary artery disease, pulmonary embolism, and aortic dissection-the so-called triple ruleout, according to Dr. U. Joseph Schoepf, director of CT research and development at Medical University of South Carolina. One comprises those who, based on clinical judgment, will leave the hospital. Scanning these people simply increases costs and radiation exposure. The other consists of those who have clear ECG signs or enzyme elevations for myocardial infarction.
Where the triple ruleout is valuable is in the gray zone: patients who have acute coronary syndrome but whose presentation is not clear-cut. They may have a nondiagnostic ECG or markers that come back negative. Without the triple ruleout, these individuals would be admitted for an extended period of observation. They would undergo serial ECGs, serial enzyme tests, and possibly other nuclear medicine tests or catheter angiography.
"If the coronary CT is negative, we can conclude that it excludes significant artery disease as a cause of acute chest pain. The negative predictive value is as high as 98% to rule out stenosis. With 64-slice CT, we are more confident than ever," Schoepf said.
