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CT-Derived FFR in the ED
Study Questions:
Can computed tomography-derived fractional flow reserve (FFRCT) enhance the evaluation of patients with acute chest pain in the emergency department (ED)?
Methods:
Patients presenting to an ED with acute chest pain between September 2015 and February 2018 underwent coronary computed tomography angiography (CCTA). Patients had no known coronary artery disease, no ischemic electrocardiographic changes, and no positive cardiac biomarkers. The study included patients with 25-99% stenosis on CCTA. FFRCT was recommended for patients with coronary stenosis >50%, coronary stenosis <50% plus high-risk plaque features, or dense coronary calcification obscuring the lumen. The ED physician or cardiologist assigned to the patient was responsible for clinical decisions; physicians were encouraged to make decisions based on standard clinical criteria due to lack of established evidence for using FFRCT for triage in acute chest pain. Follow-up continued for 90 days after index CCTA. Multiple study endpoints of feasibility, safety, clinical outcomes, and economic cost were defined and analyzed retrospectively.
Results:
A total of 555 patients with 25-99% stenosis on CCTA was included in the study. Of these, 297 patients underwent FFRCT. FFRCT results were positive in 34%. Coronary stenosis >50% was present in 82% of the FFRCT group and in 33% of the CCTA-only group. Feasibility endpoints showed that 1) adequate image quality was obtained in 98.2% of 327 scans initially selected for FFRCT, 2) median turnaround time for FFRCT declined from 12.6 hours to 2.5 hours due to a change in the processing algorithm, and 3) mean length of stay in the ED did not differ between the CCTA and FFRCT groups (16.8 hours vs. 15.5 hours; p = 0.12). A safety endpoint showed no death or myocardial infarction in the FFRCT group. Four patients had recurrent symptoms followed by late unexpected revascularizations. Clinical outcomes showed 1) no difference in major adverse cardiac events at 90 days between the CCTA and FFRCT groups (4.3% vs. 2.7%; p = 0.310) and 2) failure of diagnostic work-up in 5 (1.68%) patients in the FFRCT group and 5 (1.9%) patients in the CCTA group (p = 1.000). Cost analyses showed 1) no statistically significant difference in overall 90-day costs between the CCTA and FFRCT groups ($8,582 vs. $8,048; p = 0.550), 2) lower mean costs in patients with negative FFRCT versus CCTA alone for those with 51-70% stenosis ($3,514 vs. $9,422) and for those with >70% stenosis ($4,678 vs. $14,448), and 3) significantly lower mean costs in patients with negative FFRCT compared with those with positive FFRCT ($4,476 vs. $14,534; p < 0.001) without regard to stenosis severity.
Conclusions:
In the evaluation of ED patients with acute chest pain, utilization of FFRCT is feasible; compared with CCTA alone, there was no overall difference in safety, clinical outcomes, or costs during a 90-day follow-up period. Negative FFRCT is associated with much lower overall costs in patients with stenosis >50% or in patients with positive FFRCT. Future studies should prospectively evaluate safety and effectiveness of an FFRCT-guided triage algorithm.
Perspective:
CCTA expedites rapid triage of patients with acute chest pain in the ED and has been associated with lower length of stay and costs compared with standard care. However, CCTA may not reliably predict hemodynamic significance in patients with intermediate stenosis (51-70%), calcification, or complex plaque morphology. FFRCT is of known benefit in assessing hemodynamic significance of stenoses in chronic ischemic heart disease. This study shows that FFRCT is feasible and safe in the evaluation of acute chest pain in comparison with CCTA alone. Furthermore, costs may be substantially reduced for patients whose FFRCT results are negative.
Keywords: Tomography, X-Ray Computed, Coronary Angiography, Hemodynamics, Emergency Service, Hospital, Chest Pain, Coronary Stenosis, Constriction, Pathologic, Myocardial Ischemia, Triage
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