The prognostic value of ECG-gated SPECT imaging in patients undergoing stress Tc-99m sestamibi myocardial perfusion imaging

Abstract

Background The ability of stress radionuclide myocardial perfusion imaging to predict adverse cardiac events is well accepted. As left ventricular systolic function has also been shown to be an important prognostic indicator, the objective of this study was to determine whether electrocardiography (ECG)–gated single photon emission computed tomography (SPECT) functional data add additional power. Methods and results In this study 3207 patients who underwent stress myocardial perfusion imaging with ECG gating, without early (≤60 days) revascularization, were studied. Subsequent nonfatal myocardial infarction and cardiac death were related to perfusion and ECG-gated SPECT ventricular function parameters. Cox proportional hazards regression analysis was used to evaluate the independent predictive value of these parameters, as well as their added utility over clinical and ECG parameters. Patients with abnormal perfusion images had an annual event rate of 5.1% compared with 1.6% for patients with normal images ( P < .001). An abnormal gated SPECT wall motion score was associated with an annual event rate of 6.1% compared with 1.6% for a normal score ( P < .001), and an abnormal left ventricular ejection fraction was associated with an event rate of 7.4% compared with 1.8% for normal patients ( P < .001). Abnormal ECG-gated SPECT results worsened outcome in both patients with normal perfusion images and those with abnormal perfusion images. Cardiac death was predicted by the number of territories with a perfusion defect and an abnormal ejection fraction, whereas myocardial infarction was predicted by the number of territories with a perfusion defect but not by ejection fraction. Conclusions Ventricular function data from ECG-gated SPECT add important prognostic value to data obtained from perfusion imaging alone in predicting adverse cardiac events.