Dobutamine stress electrocardiography-gated Tc-99m tetrofosmin SPECT for detection of viable but dysfunctional myocardium

Background. Technetium-99m-labeled myocardial perfusion tracers allow simultaneous assessment of myocardial perfusion and left ventricular function by electrocardiography-gated scan. This study was performed to determine whether dobutamine stress electrocardiography-gated tetrofosmin single photon emission computed tomography (SPECT) can identify viable (as defined by positron emission tomography [PET]) but dysfunctional myocardium with contractile reserve. Methods and Results. Thirty-five patients with myocardial infarction underwent resting electrocardiography-gated SPECT and fluorodeoxyglucose (FDG) PET. The relative uptakes of tetrofosmin (%tetrofosmin) and FDG (%FDG) were calculated. Wall motion in 9 left ventricular segments was assessed at rest and during dobutamine stress on a 3-dimensional cine-mode display created with automatic left ventricular function analysis software. A total of 129 dysfunctional segments were analyzed. Forty-five (48.9%) of 92 segments with %tetrofosmin of 50% or greater and only 4 (10.8%) of 37 segments with %tetrofosmin less than 50% had contractile reserves (P < .0001). The sensitivity, specificity, and predictive accuracy of %tetrofosmin of 50% or greater for detecting %FDG of 50% or greater were 85.7%, 74%, and 82.9%, respectively. The incidence of the presence of contractile reserve rose with increasing magnitude of %FDG. The sensitivity, specificity, and predictive accuracy of the presence of contractile reserve for detecting %FDG of 50% or greater were 43.9%, 80.6%, and 52.7%, respectively. Conclusions. Dobutamine stress electrocardiography-gated SPECT can identify viable (as defined by PET) but dysfunctional myocardium with contractile reserve.