Source: U. Joseph Schoepf, MD

Coronary CT angiography (CCTA)-based triage of low-risk patients with acute chest pain in the emergency department (ED) might reduce invasive catheterizations, could improve survival and may save money, based on a study in the American Journal of Roentgenology.

Uncertainty exists as to whether CCTA compared with standard of care is more effective and efficient in the triage of low-risk ED patients with acute chest pain, according to the study authors. Therefore, Alexander K. Goehler, MD, MPH, from the Institute for Technology Assessment, Massachusetts General Hospital in Boston, and colleagues sought to construct a simulation model to estimate clinical and economic outcomes.

The researchers constructed a microsimulation model comparing standard of care to CCTA-based triage of 1,000 55-year-old patients (50 percent men) with acute chest pain, non-significant ECG changes and initial negative cardiac markers. In the standard of care arm, patients were re-evaluated with serial cardiac markers after six to eight hours, followed by either SPECT or stress echocardiography. In the CCTA-based triage arm, patients were imaged immediately and, depending on the results, discharged, held for SPECT or stress echocardiography or referred directly to invasive coronary angiography.

Compared with standard of care, CCTA-based triage reduced the number of patients referred for invasive coronary angiography from 406 (SPECT) or 370 (stress echocardiography) to 255 per 1,000 and resulted in fewer "missed" cases of acute coronary syndrome overall (five vs. 18), the authors reported.

Goehler and colleagues wrote that CCTA-based triage also resulted in fewer deaths (four vs. six). CCTA led to immediate discharge of 706 patients and produced average cost-savings in the ED of $851 (SPECT) or $462 (stress echocardiography) per patient.  At 30 days after initial ED triage, CCTA-based management produced average savings of $283 (SPECT) and average costs of $292 (stress echocardiography) per patient triaged.

The researchers chose a 30-day time horizon because a “longer time horizon would require further assumptions about the patient's and physician's future behavior regarding subsequent ED visits for recurrent chest pain within two years after an initial negative CCTA examination."

“Although CCTA had even more favorable clinical and economic outcomes at the lower end than at the upper end of underlying CAD [coronary artery disease] prevalence, it is important to note that these boundaries were derived for a middle-aged group of low-to-intermediate risk patients only; further extrapolating to an even lower prevalence of CAD should be cautioned against because this would most likely reflect a group of very low-risk patients that this model did not intend to target,” the authors wrote.

To further investigate the effect of CCTA accuracy and correctly classify the level of stenoses and the effect of undiagnosed non-STEMI and unstable angina, they conducted extreme case scenarios that would assess potential boundaries.

For the "favorable to CCTA scenario," the researchers used a combination of the most precise measures for CCTA accuracy and the upper bound (i.e., the higher mortality risk) for undiagnosed non-STEMI and unstable angina. For the "unfavorable to CCTA scenario," they used the combination of the least precise measures for CT accuracy, and the lower bound for the risk associated with missing a case of non-STEMI or unstable angina.