Abstract 5754: Cardiac CT Angiography vs. SPECT Perfusion Imaging for the Evaluation of Patients with Acute Chest Pain
BACKGROUND: Over 5 million individuals present to EDs with acute chest pain each year, many of which are hospitalized for serial EKGs and cardiac enzymes followed by stress SPECT imaging. A potential alternative to SPECT is cardiac CT, which provides for the immediate and direct evaluation of coronary artery patency. We sought to determine the concordance between these modalities and the ability of CT to exclude ischemia in patients presenting with acute chest pain.
METHODS: We enrolled 368 subjects without a history of hemodynamically significant CAD who presented to the ED with acute chest pain yet had negative initial EKGs and cardiac enzymes. All subjects underwent 64-slice cardiac CTA, the results of which were blinded to caregivers, then were admitted for standard care including diagnostic testing, as deemed clinically warranted by the caregivers. CTA exams were scored as being diagnostically positive or negative for significant stenosis (>50% luminal narrowing) or as non-diagnostic. SPECT exams were scored as diagnostically pos or neg for ischemia or scar or as non-diagnostic (e.g., secondary to submaximal workload or artifact).
RESULTS: 151 of the 368 subjects (54±11 yrs, 56% men) had an exercise (n=109), adenosine (n=41), or dobutamine (n=1) SPECT exam as part of their clinical care. 115 (76%) of the SPECT exams were read as diagnostic (7 pos for ischemia, 2 pos for scar, and 106 neg), while 36 (24%) were non-diagnostic. In contrast, 135 of the 151 (89%) of the CT exams were read as diagnostic (17 pos, 118 neg), while only 16 (11%) were non-diagnostic (p <0.001). Among the 105 patients that had both diagnostic CT and SPECT exams, there was agreement between the modalities in 97/105 (92%) of patients. With SPECT defined as the standard for detecting ischemia, absence of significant stenosis on a diagnostic CT had a 98% NPV for excluding ischemia.
CONCLUSION: Cardiac CT appears to be as feasible as SPECT imaging in patients with acute chest pain but inconclusive initial ED evaluation and may have a lower rate of non-diagnostic exams. Consistent with the known high NPV of CCT, absence of significant stenosis on cardiac CT predicted the absence of SPECT based ischemia in 98% of subjects. Thus, cardiac CT may be sufficient to exclude ischemia in patients with acute chest pain.