FFR by CT Angiography to Identify Ischemia
What is the association between coronary stenosis severity, plaque characteristics, coronary computed tomography angiography (CTA)-derived fractional flow reserve (FFRCT), and lesion-specific ischemia identified by FFR?
Coronary CTA stenosis, plaque volumes, FFRCT, and FFR were assessed in 484 vessels from 254 patients. Stenosis >50% was considered obstructive. Plaque volumes (noncalcified plaque [NCP], low-density NCP [LD-NCP], and calcified plaque [CP]) were quantified using semi-automated software. Optimal thresholds of quantitative plaque variables were defined by area under the receiver-operating characteristic curve (AUC) analysis. Ischemia was defined by FFR or FFRCT ≤0.80.
Plaque volumes were inversely related to FFR irrespective of stenosis severity. Relative risk (95% confidence interval) for prediction of ischemia for stenosis >50%, NCP ≥185 mm3, LD-NCP ≥30 mm3, CP ≥9 mm3, and FFRCT ≤0.80 were 5.0 (3.0–8.3), 3.7 (2.4–5.6), 4.6 (2.9–7.4), 1.4 (1.0–2.0), and 13.6 (8.4–21.9), respectively. Low-density NCP predicted ischemia independent of other plaque characteristics. Low-density NCP and FFRCT yielded diagnostic improvement over stenosis assessment with AUCs increasing from 0.71 by stenosis >50% to 0.79 and 0.90 when adding LD-NCP ≥30 mm3 and LD-NCP ≥30 mm3 + FFRCT ≤0.80, respectively.
The authors concluded that stenosis severity, plaque characteristics, and FFRCT predict lesion-specific ischemia.
This study reports that coronary stenosis severity, plaque characteristics, and FFRCT all predict lesion-specific ischemia. The addition of coronary atherosclerotic plaque and FFRCT assessment appears to improve the discrimination of ischemia compared with stenosis evaluation alone. These findings suggest that a comprehensive anatomical–physiological approach combining coronary CTA anatomical stenosis assessment with semi-automated quantification of plaque volumes and FFRCT computation may be a useful strategy for noninvasive assessment of stable coronary artery disease and potentially more effectively triage patients that need to go to the catheterization laboratory.
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