This prospective, multicenter, randomized, strategy-controlled trial was designed primarily to assess whether CCTA, incorporated early into an evaluation strategy for patients presenting to an emergency department with chest pain suggestive of an acute coronary syndrome, safely improves the efficiency of clinical decision making, as compared with a standard evaluation in the emergency department. The cumulative costs of diagnostic tests, interventions, and radiation exposure were also evaluated. The average length of stay in the hospital, the primary end point of the trial, was significantly reduced in the CCTA group, as was the time to diagnosis. Furthermore, rates of direct discharge from the emergency department were higher with CCTA than with a standard evaluation in the emergency department. These results were achieved without putting patients at greater risk for undetected acute coronary syndromes and without an increase in the cost of care. However, we observed increased diagnostic testing in the CCTA group and increased radiation exposure.
An important consideration when results show more efficient triage is whether that gain is achieved at the risk of undetected acute coronary syndromes. There were no undetected cases of acute coronary syndromes in either study group, suggesting that the earlier and greater number of discharges in the CCTA group did not result in any missed diagnoses. More major adverse cardiovascular events were observed in the standard-evaluation group than in the CCTA group, though the study did not have the statistical power to support the conclusion that major adverse cardiovascular events may be reduced after a CCTA-based evaluation.
The prevalence of acute coronary syndromes in a patient population is an important determinant of the risk–benefit ratio, given that CCTA is an advanced diagnostic imaging test that entails the administration of iodinated contrast material, radiation exposure, and costs. In our study population of patients who were at intermediate risk for acute coronary syndromes (observed rate of acute coronary syndromes, 7.5%, vs. 2 and 4% in previous studies10,11
), a greater number of invasive coronary procedures were performed after CCTA than after a standard evaluation. Information on the presence of anatomical coronary artery disease may influence clinical decision making toward invasive angiography. This concept is consistent with recent data suggesting that in a Medicare population, imaging of the coronary anatomy with CCTA in a nonemergency setting led to greater use of downstream testing and procedures, as compared with functional stress testing.12
In this trial, no decrease in total costs for the index visit and during 28-day follow-up was observed in a subgroup of 649 patients from five of nine sites in which complete billing data were available. Long-term outcome data are not available; such data might have allowed a determination of whether CCTA results in fewer repeat visits to the emergency department and hospitalizations over a longer time course.
Cumulative radiation exposure was higher in the group randomly assigned to CCTA than in the standard-evaluation group. Recent data show that diagnostic-quality CCTA imaging can be performed with exposure of less than 5 mSv in selected patients; this suggests that future studies could use lower doses of radiation.16,17
Lower-dose radiation should be considered in efforts to apply this strategy more widely, as well as in particular groups of patients.
There are several limitations of the present study and analysis. Enrollment occurred only during weekday hours when all imaging testing was available with technologists and readers on site. However, the results of triage decision making and particularly the timing of decisions to discharge or hospitalize patients would probably be different if the imaging studies were carried out during the night, when testing and interpretation are not as accessible. Similarly, the results cannot be generalized to clinical sites that perform a dedicated accelerated diagnostic protocol18
in the standard evaluation.
Inherent in the design of any randomized, comparative-effectiveness trial assessing a testing procedure is the lack of blinding to the intervention. We acknowledge that there may have been a bias in decision making toward earlier discharge in the CCTA group. For both groups of patients, however, the decision making was left to a large number of clinicians at the nine sites who were not directly associated with the study and whose decisions were subject to the same imperatives to provide high-quality clinical care and to take into account medical and legal considerations. Finally, the results of this study may not be applicable to populations that we did not study, including patients younger than 40 years of age and those older than 74 years of age.
In conclusion, in this trial involving patients with suspected acute coronary syndromes, an evaluation strategy incorporating early CCTA, as compared with a standard evaluation strategy, improved the efficiency of clinical decision making for triage in the emergency department, with a shorter length of stay in the hospital and more direct discharges from the emergency department. This improvement appeared to be accomplished safely, without putting patients at greater risk for undetected acute coronary syndromes. There was increased diagnostic testing and higher radiation exposure in the CCTA group, with no overall reduction in the cost of care. These data should allow providers and patients to make informed decisions about the use of this technology as an option for evaluation when symptoms are suggestive of an acute coronary syndrome.