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SPECT With Stress-Only Imaging vs. CTA for Acute Chest Pain
Study Questions:
Several randomized trials have compared coronary computed tomography angiography (CCTA) with usual care or a stress testing in both acute and stable chest pain and have demonstrated reduced time to discharge, and in some cases, lower radiation exposures and costs. Conversely, recent data have demonstrated that stress-first SPECT myocardial perfusion imaging (MPI) can lower costs, decrease radiation exposure, and accelerate time to diagnosis. Are modern stress-first SPECT MPI protocols comparable to CCTA for evaluating patients with acute chest pain?
Methods:
This was a randomized controlled trial comparing SPECT MPI (without attenuation correction) using a stress-first protocol to CCTA among adult patients hospitalized under observation status for acute chest pain in one academic medical center. The primary endpoint was length of hospitalization. Radiation exposures and cost data were also collected. Clinical event data (cardiac death, nonfatal myocardial infarction, or unstable angina) were obtained over a median of 6.4 months.
Results:
Out of 2,994 potential patients, 57% were not candidates for CCTA and were not eligible for randomization. Of the remaining 1,003 patients, 405 did not consent, 310 were randomized to SPECT MPI, and 288 to CCTA. Although all SPECT patients had stress-first SPECT imaging, 96% (n = 296) were normal, and only 27% had stress-only imaging. The remainder required both stress and rest imaging. Mean time to diagnosis was slightly shorter for CCTA than SPECT (8.1 vs. 9.4 hours, p = 0.0002), but length of stay was substantially shorter for CCTA (19.7 vs. 23.5 hours, p = 0.0002). However, stress-only SPECT and normal CCTA both had equivalent time to diagnosis (7.0 vs. 6.8 hours, p = 0.20) and length of stay (15.5 vs. 167 hours, p = 0.36). Among all patients, CCTA was associated with higher radiation exposure (12.7 vs. 10.9 mSv, p < 0.0001). Stress-only SPECT MPI was associated with markedly lower radiation (5.5 mSv, p < 0.0001). Costs were lower by $862 per patient with CCTA than SPECT (p = 0.006) for all patients, but were comparable for stress-only SPECT (p = 0.86). Twenty-two patients experienced cardiac events (3.8%). While both SPECT and CCTA had reasonable sensitivity for events (78% vs. 85%, p = 1.0), SPECT had substantially higher specificity (99% vs. 92%, p < 0.0001) and overall accuracy (98% vs. 91%, p < 0.0001).
Conclusions:
Stress SPECT with optimized stress-only imaging is comparable to CCTA in time to diagnosis, length of stay, and cost, and also has higher diagnostic accuracy and lower radiation exposure. Optimized SPECT is associated with longer time to diagnosis and length of stay and costs.
Perspective:
This study adds additional data in the face of multiple randomized clinical trials comparing CCTA versus stress testing or usual care in acute chest pain. The differences between this study and prior studies are the mandated use of SPECT in the control arm rather than a mixture of stress testing and clinical management choices in many prior studies. Furthermore, a modern stress-first protocol was used. However, only a minority of patients underwent stress-only imaging in this study. In general, most patients with normal stress tests can have excellent diagnostic and prognostic accuracy with stress-only imaging. In order to maximize the efficacy of the stress-first approach, attenuation correction or another strategy such as supine and prone imaging is required to minimize artifacts that result in a need for rest imaging for comparison. This study did not use SPECT-CT for attenuation correction. Additionally, no mention is made of using prone imaging, which can be done in less than 10 minutes on modern ultrafast scanners.
Another important conclusion of this study is that a majority of screened patients (57%) were ineligible due to ineligibility for CCTA, suggesting that SPECT MPI is much more versatile in clinical practice. These reasons included contraindications to CCTA (e.g., renal dysfunction, allergies to contrast media, and arrhythmias) as well as populations in which CCTA was likely to have poorer diagnostic performance (e.g., prior history of coronary artery disease and cardiomyopathy).
Keywords: Acute Coronary Syndrome, Angina, Unstable, Angiography, Chest Pain, Diagnostic Imaging, Exercise Test, Myocardial Infarction, Myocardial Perfusion Imaging, Radiation, Tomography, Emission-Computed, Single-Photon, Tomography, X-Ray Computed
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