Role of perfusion myocardial scintigraphy with gated SPECT technique in the diagnostic and prognostic evaluation of patients with chronic coronary disease

The acquisition of perfusion scintigraphy using gated single-photon emission computed tomography (SPECT) is an important development of nuclear medicine. Gated SPECT allows the automated calculation of left ventricular ejection fraction (LVEF) and the assessment of regional function using perfusion images. A good correlation exists between resting gated SPECT and other imaging techniques for the calculation of LVEF and the assessment of regional wall motion and thickening. The simultaneous assessment of perfusion and function is helpful for the diagnostic and prognostic assessment of patients with chronic coronary artery disease. The addition of functional data to stress and rest perfusion images significantly improves their specificity and reduces the uncertainty in test interpretation, with a better separation of normal from abnormal studies. The post-stress ejection fraction value provides incremental prognostic information over myocardial perfusion evaluation. Post-stress ejection fraction is the most significant predictor of cardiac death whereas the extent of ischemia is the best predictor of nonfatal myocardial infarction. Thus, the integration of perfusion and function improves the stratification of patients into low, intermediate and high-risk groups for coronary events. Moreover, gated SPECT is a novel interesting method to identify myocardial viability, because it can provide in a single stress study information about degree of regional asynergy, segmental tracer uptake, regional contractile reserve and changes in LVEF during inotropic stimulation, obviating the need for separate tests to assess reversible dysfunction. Regional dysfunction assessment directly on perfusion images permits to use different activity thresholds for viability recognition in adyskinetic versus hypokinetic segments, with an improvement over the use of a single cut-off for all asynergic segments. The acquisition of gated SPECT images during low-dose dobutamine infusion permits the detection of contractile reserve in asynergic segments. The assessment of contractile reserve increases the diagnostic accuracy of perfusion imaging and the combination of perfusion and functional data significantly improves the accuracy of gated SPECT in detecting viable hibernating myocardium. Finally, the increase in ejection fraction during low-dose dobutamine stimulation is a strong predictor of the improvement in LVEF after revascularization. In conclusion, together with myocardial perfusion assessment, gated SPECT gives additional data that have important implications for the optimal management of patients with chronic coronary artery disease.