Comparison of myocardial perfusion imaging and cardiac troponin I in patients admitted to the emergency department with chest pain

Background-Identification of patients with acute coronary syndromes (ACS) a mong those who present to emergency departments with possible myocardial is chemia is difficult. Myocardial perfusion imaging with Tc-99m sestamibi and measurement of serum cardiac troponin I (cTnI) both can identify patients with ACS. Methods and Results-Patients considered at low to moderate risk for ACS und erwent gated single-photon emission CT sestamibi imaging and serial myocard ial marker measurements of creatine kinase-MB, total creatine kinase activi ty, and cTnI over 8 hours. Positive perfusion imaging was defined as a perf usion defect with associated abnormalities in wall motion or thickening. cT nI greater than or equal to 2.0 ng/mL was considered abnormal. Among the 62 0 patients studied, 59 (9%) had myocardial infarction and 81 (13%) had sign ificant coronary disease; of these patients, 58 underwent revascularization . Perfusion imaging was positive in 241 patients (39%), initial cTnI was po sitive in 37 (6%), and cTnI was greater than or equal to 2.0 ng/mL in 74 (1 2%), Sensitivity for detecting myocardial infarction was not significantly different between perfusion imaging (92%) and cTnI (90%), and both were sig nificantly higher than the initial cTnI (39%). Sensitivity for predicting r evascularization or significant coronary disease was significantly higher f or perfusion imaging than for serial cTnI, although specificity for all end points was significantly lower. Lowering the cutoff value of cTnI to 1.0 n g/mL did not significantly change the results. Conclusions-Early perfusion imaging and serial cTnI have comparable sensiti vities for identifying myocardial infarction. Perfusion imaging identified more patients who underwent revascularization or who had significant corona ry disease, but it had lower specificity. The 2 tests can provide complemen tary information for identifying patients at risk for ACS.