Coronary plaque quantification and fractional flow reserve by coronary computed tomography angiography identify ischaemia-causing lesions

Abstract

AimsCoronary plaque characteristics are associated with ischaemia. Differences in plaque volumes and composition may explain the discordance between coronary stenosis severity and ischaemia. We evaluated the association between coronary stenosis severity, plaque characteristics, coronary computed tomography angiography (CTA)-derived fractional flow reserve (FFRCT), and lesion-specific ischaemia identified by FFR in a substudy of the NXT trial (Analysis of Coronary Blood Flow Using CT Angiography: Next Steps).Methods and resultsCoronary CTA stenosis, plaque volumes, FFRCT, and FFR were assessed in 484 vessels from 254 patients. Stenosis >50% was considered obstructive. Plaque volumes (non-calcified 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 characteristics curve (AUC) analysis. Ischaemia 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 ischaemia 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 ischaemia 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.ConclusionStenosis severity, plaque characteristics, and FFRCT predict lesion-specific ischaemia. Plaque assessment and FFRCT provide improved discrimination of ischaemia compared with stenosis assessment alone.

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“…FFRCT <0.80 was considered diagnostic of lesion specific ischaemia. A report said that low-density non-calcified plaque (LD-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 mm 3 and LD-NCP ≥30 mm 3 + FFRCT ≤0.80, respectively (24). However, whether CCTA image can display the actual vascular elasticity still needs to be explored.…”

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“…Recently, it has been shown that the presence of high-risk plaque features, especially large low attenuation plaque, a CTA surrogate for necrotic core, is strong predictor of FFR-verified ischemia independent of degree of luminal stenosis. 102,103 Local impairment of the vessel to dilate at the site of a stenosis with either a large plaque burden or necrotic core, a hallmark of vulnerable plaque, may contribute to ischemia independent of the degree of luminal narrowing. In this regard, plaques with large necrotic cores are often significantly positively remodeled, even if the lumen is not significantly narrowed.…”

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“…19 The presence of low-density non-calcified plaque (≥30 mm 3 ) and FFR CT (≤0.80) increased significantly the diagnostic accuracy of coronary stenoses to detect lesion-specific ischemia (as assessed by invasive FFR), documented by an increase in the area under the receiver operating characteristic curve from 0.71 to 0.90 (P < 0.001). The non-randomized Prospective LongitudinAl Trial of FFR CT : Outcome and Resource IMpacts (PLATFORM) trial assessed the impact of FFR CT on clinical outcomes, downstream resource utilization and costs in two parallel observational arms, one with an intended invasive strategy (n = 380) and one with planned non-invasive testing (n = 204).…”