Diagnostic performance of the quantitative flow ratio and CT-FFR for coronary

The present study demonstrated that the QFR and CT-FFR are strongly correlated with the FFR. The QFR and CT-FFR can provide excellent clinical diagnostic performance for coronary lesion-specific ischemia detection. Therefore, the QFR and CT-FFR can serve as tools to guide clinical practice in determining coronary lesion-specific ischemia. This study provides key data for the clinical application of the QFR and CT-FFR in patients with CAD.

The ICA is the most widely used method for guiding PCI in patients with CAD. However, physician assessments of CAD severity cannot satisfactorily distinguish between significantly functional lesions and nonsignificant functional lesions. There are studies indicating that the relationship between the severity of quantitative stenosis on coronary angiography and the level of functional blood flow restriction is weak^17,18. A simple percentage description of a narrowed coronary artery does not necessarily represent the full physiological impact on its perfused myocardium¹⁹. The FFR has the ability to measure myocardial ischemia induced by lesions via a pressure wire under maximum hyperemic conditions (adenosine administration). Compared with visual angiography, physiological measurements based on pressure wires can more accurately identify blood flow-limiting lesions in patients with CAD. The FFR is considered the gold standard for detecting coronary lesion-specific ischemia and is strongly supported in guiding revascularization decisions²⁰. The FAME trial followed up for 1 year, and the FAME 2 trial followed up for 3 years and reported that FFR-guided PCI can significantly reduce major cardiovascular events^21,22. Although there is scientific evidence suggesting that coronary artery revascularization based on functional assessment is beneficial, the application of the FFR still remains significantly underutilized²³. However, according to a recent study, the use of the FFR in patients with intermediate lesions in the United States has increased slowly but steadily from 14.8 to 18.5% in recent years²⁴.

The QFR is obtained through coronary angiography imaging and does not require pressure guide wires or hyperemic agents²⁵. The acquisition of the QFR is very fast in the catheterization laboratory (median 266 s)²⁶. Therefore, compared with the FFR, the QFR can reduce the procedure time, risk, contrast agent, radiation exposure and costs. The QFR can help clinical physicians make decisions on coronary artery revascularization by identifying significantly functional lesions²⁷. The software used for QFR in this study was AngioPlus, and recent studies (such as the FAVOR II China study and the FAVOR III study) have confirmed its application in coronary lesions. The FAVOR II China study revealed that the diagnostic accuracy of the QFR was 92.7%, with a sensitivity of 94.6% and a specificity of 91.7%⁹. The FAVOR III study confirmed that, compared with standard angiography guidance, QFR-guided PCI can reduce the risk of 1-year major adverse cardiac events by 35%²⁸. The QFR is easier to implement than the FFR is, which helps to incorporate the QFR into routine clinical practice.

CCTA is a noninvasive and widely used clinical tool for detecting suspicious CAD. However, CCTA cannot be used to evaluate the hemodynamics of coronary artery lesions²⁹. Before performing ICA, it is necessary to evaluate the physiological function of coronary artery lesions on the basis of CCTA data. The CT-FFR is a validated noninvasive diagnostic method based on CCTA datasets that can accurately detect the hemodynamics of coronary artery lesions³⁰. In patients without significant functional lesions, the CT-FFR can reduce the number of unnecessary coronary angiographies. A prospective study confirmed that the CT-FFR can reduce the incidence of ICA by 61%³¹. The advantage of CT-FFR lies not only in its high diagnostic accuracy in detecting lesion-specific ischemia but also in not changing the CCTA data collection protocol, providing additional images, or administering medication^7,32. Therefore, the CT-FFR is a feasible and safe alternative to ICA. In this study, Coronary Scope software was used for the CT-FFR measurements. Coronary Scope is a novel deep machine learning-based software for calculating the CT-FFR for predicting coronary ischemia^12,33,34. Recently, a multicenter study from six clinical medical centers with 324 vessels from 301 patients used the Coronary Scope software to detect the diagnostic accuracy of the CT-FFR. The results showed that on a per-vessel basis, the diagnostic sensitivity, specificity, and accuracy of the CT-FFR for detecting coronary lesion-specific ischemia were 95%, 92%, and 94%, respectively. In addition, the CT-FFR values were strongly correlated with the FFR values (Spearman’s…