Resting Radionuclide Myocardial Perfusion Imaging in a Chest Pain Center Including an Overnight Delayed Image Acquisition Protocol

Emergency department (ED) patients with chest pain (CP) and a nondiagnostic electrocardiogram (ECG) present difficult management decisions. The purpose of this study was to investigate the utility of resting radionuclide SPECT myocardial perfusion imaging (SPECT MPI)-including an overnight delayed image acquisition protocol-in identifying patients presenting to the ED with CP at risk for cardiac events. Methods: Patients presenting to the ED with CP and a nondiagnostic ECG were prospectively enrolled and underwent chest pain center evaluation. All patients also underwent resting gated SPECT MPI using Tc-99m-tetrofosmin tracer. Patients presenting on weeknights between 12 AM and 6 AM had tracer injection in the ED with image acquisition delayed until later in the morning. Patients were monitored for a 30-d occurrence of cardiac events. Results: Over a 16-mo period, 479 patients were enrolled and completed follow-up. For the prediction of 30-d cardiac events, resting SPECT MPI demonstrated a sensitivity and a specificity of 76.9% and 92.4%, respectively. Positive and negative predictive values were 22.2% and 99.3%, respectively. Among the 3 patients with a normal perfusion scan who suffered cardiac events, all had tracer injection several hours after resolution of CP. The overnight delayed image acquisition protocol provided a negative predictive value of 100% for the 44 patients whose image acquisition was delayed until the following morning. Conclusion: A normal resting SPECT MPI in ED patients presenting with CP predicts a very low occurrence of 30-d cardiac events. A delayed image acquisition protocol did not decrease the accuracy of SPECT MPI. Such a protocol may be useful in increasing the availability of this imaging modality.