Background: We conducted an exploratory analysis to test whether the addition of a CAC scan can increase the applicability of stress-only SPECT-MPI.
Methods: We studied 162 patients referred for rest/stress SPECT-MPI who underwent a CAC scan. Each scan was interpreted by two readers in stepwise fashion: stress-only images; addition of clinical data; and addition of CAC data. At each step, the reader was asked if rest SPECT-MPI was necessary.
Results: Stress-only images were interpreted as normal in 62, probably normal in 42, equivocal in 15, probably abnormal in 5, and definitely abnormal in 38 patients. Rest SPECT-MPI imaging was considered necessary, in 0% of normal studies, but in 88% of probably normal studies, and 100% of those with equivocal/abnormal studies. Addition of the clinical data did not materially change this decision. Additional consideration of the CAC scan results did not influence the deemed lack of need for a rest SPECT-MPI with normal SPECT-MPI or the necessity of rest SPECT-MPI with abnormal SPECT-MPI. However, the CAC scan reduced the deemed need for a rest SPECT-MPI in 72% with a probably normal, 47% with an equivocal, and 40% of those with a probably abnormal SPECT-MPI.
Conclusions: Our exploratory analysis indicates that addition of a CAC scan to stress SPECT-MPI tends to diminish experienced readers' deemed need to perform rest SPECT-MPI studies among patients with probably normal or borderline stress-only SPECT-MPI studies. Thus, further study appears warranted to assess the utility of using CAC scanning as a means for increasing the percent of SPECT-MPI studies that can be performed as stress-only studies.