Sensitivity of acute rest myocardial perfusion imaging for identifying patients with myocardial infarction based on a troponin definition.

BACKGROUND: Myocardial perfusion imaging (MPI) is often used to identify low-risk chest pain patients who have myocardial infarction (MI). A recent recommendation is that patients with increased troponin levels be diagnosed as having MI. The sensitivity and characteristics of patients who have elevated troponin levels who also underwent early MPI are unknown. METHODS AND
RESULTS: Patients considered at low risk for MI underwent rest gated tomographic MPI and serial marker assessment as part of a standard chest pain evaluation protocol. Patients with cardiac troponin I (cTnI) elevations were analyzed further for this study. MPI results were considered positive if there was a perfusion defect in association with abnormal wall motion or thickening. Short-axis images were divided into 17 segments and graded on a 4-point scale (0, normal; 3, high-grade or absent perfusion), and a summed rest score was derived. Of the 319 patients who had MPI and cTnI elevations, 78 had negative MPI results (sensitivity, 75%). Patients with negative MPI results had lower peak creatine kinase (CK)-MB values (15 +/- 25 ng/mL vs 45 +/- 78 ng/mL, P <.0001) and higher ejection fractions (56% +/- 15% vs 47% +/- 13%, P <.0001) and were less likely to have significant disease (55% vs 72%, P =.04) than those with positive MPI results. Increasing summed rest score was associated with larger MIs as estimated by peak CK and CK-MB values.
CONCLUSIONS: Patients with negative MPI results have smaller MIs and less extensive coronary disease. MPI and cTnI offer complementary data for assessing patients with possible MI.