CT-Derived FFR Enables Accurate ‘Virtual Stenting’

PARIS, France—Using computed tomographic (CT) imaging to calculate fractional flow reserve (FFR) enables accurate 3-D modeling of coronary stenosis and “virtual stenting.” The technique can be used to predict the success of percutaneous coronary intervention (PCI), according to results with the technology presented Wednesday, May 16, at EuroPCR 2012.

The first major study of CT-derived FFR came with the DISCOVER FLOW trial, presented at EuroPCR 2011 and subsequently published in the Journal of the American College of Cardiology by Bon-Kwon Koo, MD, PhD, of Seoul National University Hospital (Seoul, South Korea), and colleagues. The trial showed that the new noninvasive imaging method yields high diagnostic accuracy comparable to the gold standard of invasive FFR.

For the current study, Dr. Koo and colleagues compared the accuracy of CT-derived FFR with conventional FFR before and after stenting in 44 stable patients (48 vessels) from 3 centers. To perform virtual stenting, the researchers modified the 3-D computational model generated from CT-derived FFR to restore the area of the treated coronary segment to that of the proximal and distal reference areas. The CT-FFR value was then recalculated.

Methods Show Good Correlation

Prior to PCI, conventional FFR and CT-derived FFR correlated well by showing values of 0.70 ± 0.14 and 0.70 ± 0.15, respectively, resulting in a difference of merely 0.006 ± 0.14 (R = 0.6; P < 0.01). After PCI, the values for conventional FFR and CT-derived FFR were 0.90 ± 0.05 and 0.88 ± 0.05, respectively, again showing good correlation at a difference of 0.02 ± 0.05 (R = 0.55; P < 0.01).

Upon further analysis, the disagreement between CT-derived and conventional FFR was again low, starting with a mean difference before stenting of 0.0063 and 95% confidence interval of -0.27 to 0.28, with the confidence interval narrowing further after stenting to -0.077 to 0.125. After virtual stenting, CT-derived FFR found no false-negatives and 2 false-positives (3.5%) compared with conventional FFR. There were 44 true-negatives (93%) and 2 true-positives (3.5%) on CT-FFR.

CT-derived FFR showed an overall sensitivity of 100% and specificity of 96% in predicting ischemia after stenting. Negative- and positive-predictive values were 100% and 50%, respectively, with a total accuracy rate of 96%.

“Treatment planning using virtual stenting and FFR-CT seems to be feasible,” Dr. Koo said, “and FFR-CT after virtual stenting can accurately predict the success of PCI in terms of relieving myocardial ischemia, so this novel technology may enable optimal patient- and lesion-specific treatment choice before the invasive procedure.”

Study Details

Patients had a reference vessel diameter of 3.0 ± 0.7 mm and a diameter stenosis of 64.5 ± 14.0%. The majority of patients were male (80%) with an LVEF of 63.1 ± 7.4%. After stenting, MLD was 2.6 ± 0.5 mm, with a stent diameter of 3.1 ± 0.4 mm and a stent length of 26.0 ± 10.1 mm. Diameter stenosis was 10.1 ± 8.5%.

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Source:
Koo B-K. A novel non-invasive technology for treatment planning using virtual coronary intervention and CT-derived computed fractional flow reserve (FFR_CT). Presented at: EuroPCR; May 16, 2012; Paris, France. 

Disclosure:

• Dr. Koo reports no relevant conflicts of interest.

Related Stories:

• DISCOVER-FLOW Published: Noninvasive FFR Shows High Diagnostic Accuracy
• DISCOVER-FLOW: CT-Derived FFR Measurements Show High Diagnostic Accuracy

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