Background

Fractional flow reserve (FFR) is currently the gold standard for assessment of coronary lesion-specific ischemia. Virtual fractional flow reserve (vFFR) derived from coronary computed tomography angiography (CTA), which is based on a parallel computing method which does not require a supercomputer, is a novel on-site technique that is extremely fast and fully automated.

Methods

We analyzed 100 vessels from 57 patients who had undergone a CTA followed by invasive FFR during coronary angiography (ICA). Coronary lumen segmentation and 3-D reconstruction were conducted by using a completely automated algorithm without any operator intervention. Parallel computing based vFFR prediction was also performed. Lesion-specific ischemia based on FFR were defined as significant at≤ 0.8 as well as≤ 0.75 and obstructive CTA stenosis was defined by≥ 50%. The diagnostic performance of vFFR was compared to invasive FFR at both≤ 0.8 and≤ 0.75.

Results

The average computation time was 12 minutes per patient. Correlation coefficient (r) between vFFR and invasive FFR was 0.75 (95% CI 0.65 to 0.83) and Bland-Altman analysis showed a mean bias of 0.005 (95% CI-0.011 to 0.021) with 95% limits of agreement− 0.16 to 0.17 between vFFR and FFR. The accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 78.0%, 87.1%, 72.5%, 58.7%, and 92.6%, respectively using the FFR cutoff of 0.80. They were 87.0%, 95.0%, 80.0%, 54.3%, and 98.5%, respectively with an FFR cutoff of 0.75. The area under the receiver-operating characteristics curve of vFFR vs. obstructive CTA stenosis was 0.88 vs. 0.61 for the FFR cutoff of 0.80. It was 0.94 vs. 0.62 for the FFR cutoff of 0.75.

Conclusion

This novel on-site vFFR technology, which is based on a fully automated segmentation algorithm and parallel computation, is time-saving, cost effective, and shows an excellent diagnostic performance for detection of lesion-specific ischemia.