Influence of the postexercise acquisition delay on the detection of functional abnormalities in sestamibi-gated SPECT.

Gated single photon emission computed tomography (SPECT) identifies functional changes produced by ischemia, but the influence of acquisition delay on their detection is not established. Methods and Results: In 80 patients with known or suspected coronary artery disease, gated SPECT was acquired twice: first, less than 30 minutes after peak exercise (stress 1), and second, more than 45 minutes after peak exercise (stress 2). End-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) were compared with perfusion. The relationship between the ΔEF (stress EF - resting EF) and the summed difference score (SDS) was -0.443 (P < .0001) for stress 1 and -0.416 (P < .0001) for stress 2. In stress 1, EF increased in patients without inducible ischemia (SDS = 0) (57% ± 10% vs 54% ± 9% at rest, P < .02) and decreased in those with an SDS of 1 or greater (53% ± 10.8% vs 55% ± 9.6% at rest, P < .05). In stress 2, EF was unchanged in patients without ischemia (55.8% ± 9.7%, P = .06) and decreased in the other patients (52.8% ± 10.2%, P < .01). In patients without ischemia, both the EDV and ESV decreased significantly in stress 1 and were unchanged in stress 2. In patients with an SDS of 1 or greater, the EDV remained unchanged and the ESV minimally decreased in stress 1, whereas both volumes clearly and significantly increased in stress 2. Conclusions: The early acquisition of postexercise gated SPECT is slightly more effective in detecting ischemia-related functional changes; however, a delayed acquisition within 60 minutes still permits the detection of functional abnormalities in most patients.