Meta-Analysis of Diagnostic Performance of Instantaneous Wave-Free Ratio versus Quantitative Flow Ratio for Detecting the Functional Significance of Coronary Stenosis

Predictive value of intravascular ultrasound for the function of intermediate coronary lesions

BACKGROUND

Intravascular ultrasound (IVUS) can provide detailed coronary anatomic parameters. The purpose of our study was to evaluate the parameters measured by IVUS for the prediction of intermediate coronary lesions function by referencing quantitative fraction ratio (QFR) ≤ 0.80 (vs. > 0.80).

METHODS

Eighty four cases with 92 intermediate coronary lesions in vessels with a diameter ≥ 2.50 mm were enrolled. Paired assessment of IVUS and cQFR was available, and vessels with cQFR ≤ 0.8 were considered the positive reference standard. Logistic regression was used to select model variables by a maximum partial likelihood estimation test and receiver operating characteristic curve (ROC) analysis to evaluate the diagnostic value of different indices.

RESULTS

Plaque burden (PB) and lesion length (LL) of IVUS were independent risk factors for the function of coronary lesions. The predictive probability P was derived from the combined PB and LL model. The area under the curve (AUC) of PB, (minimum lumen area) MLA, and LL and the predicted probability P are 0.789,0.732,0731, and 0.863, respectively (P < 0.01). The AUC of the predicted probability P was the biggest among them; the prediction accuracy of cQFR ≤ 0.8 was 84.8%, and the sensitivity of the diagnostic model was 0.826, specificity was 0. 725, and P < 0.01.

CONCLUSION

PB and LL of IVUS were independent risk factors influencing the function of intermediate coronary lesions. The model combining the PB and LL may predict coronary artery function better than any other single parameter.

Accuracy of the angiography-based quantitative flow ratio in intermediate left main coronary artery lesions and comparison with visual estimation

BACKGROUND

Revascularization of left main coronary artery (LMCA) stenosis is mostly based on angiography. Indices based on angiography might increase accuracy of the decision, although they have been scarcely used in LMCA. The objective of this study is to study the diagnostic agreement of QFR (quantitative flow ratio) with wire-based fractional flow reserve (FFR) in LMCA lesions and to compare with visual severity assessment.

METHODS

In a series of patients with invasive FFR assessment of intermediate LMCA stenoses we retrospectively compared the measured value of QFR with that of FFR and the estimate of significance from angiography.

RESULTS

107 QFR studies were included. The QFR intra-observer and inter-observer agreement was 87% and 82% respectively. The mean QFR-FFR difference was 0.047 ± 0.05 with a concordance of 90.7%, sensitivity 88.1%, specificity 92.3%, positive predictive value 88.1% and negative predictive value 92.3%. All these values were superior to those observed with the visual estimation which showed an intra- and inter-observer agreement of 73% and 72% respectively, besides 78% with the FFR value. The low diagnostic performance of the visual estimation and the acceptable performance of the QFR index measurement were observed in all subgroups analysed.

CONCLUSIONS

QFR allows an acceptable estimate of the FFR obtained with intracoronary pressure guidewire in intermediate LMCA lesions, and clearly superior to the assessment based on angiography alone. The decision to revascularize patients with moderate LMCA lesions should not be based solely on the degree of angiographic stenosis.

Diagnostic comparison of automatic and manual TIMI frame-counting-generated quantitative flow ratio (QFR) values

Quantitative flow ratio (QFR) is a computational measurement of FFR (fractional flow reserve), calculated from coronary angiography. Latest QFR software automates TIMI frame counting (TFC), which occurs during the flow step of QFR analyses, making the analysis faster and more reproducible. The objective is to determine the diagnostic performance of QFR values obtained from analyses using automatic TFC compared to those obtained from analyses using manual TFC. This was a single-arm clinical trial that used the prospective analysis of the coronary angiographic image series of 97 patients who underwent evaluation of stable coronary artery disease with FFR/iFR at MedStar Washington Hospital Center in Washington, DC, USA. Automatic and manual TFC QFR values were obtained from the analyses of each of the 97 patients' image series, with manual TFC QFR values as the current gold standard for comparison. The diagnostic performance of automatic TFC QFR values was measured as follows: sensitivity was 0.87 (95% CI 0.66-0.97) and specificity was 1.00 (95% CI 0.9514-1.00), positive predictive value (PPV) was 1.00 (95%CI 1.00-1.00), while the NPV was 0.96 (95% CI 0.96-0.99). Overall accuracy was 96.91% (95% CI 91.23%-99.36%). The agreement as illustrated by the Bland-Altman plot shows a bias of 0.0023 (SD 0.0208) and narrow limits of agreement (LOA): Upper LOA 0.0573 and Lower LOA - 0.0528. The area under curve (AUC) was 0.996. QFR values generated from automatic TFC are comparable to those generated from manual TFC in diagnostic capability. The most recent software update produces values equivalent to those of the previous manual option, and can therefore be used interchangeably.

Performance of Integrated Near-Infrared Spectroscopy and Intravascular Ultrasound (NIRS-IVUS) System against Quantitative Flow Ratio (QFR)

Quantitative flow ratio (QFR) is a new opportunity to analyze functional stenosis during invasive coronary angiography. Together with a well-known intravascular ultrasound (IVUS) and a new player in the field, near-infrared spectroscopy (NIRS), it is gaining a lot of interest. The aim of the study was to compare QFR results with integrated IVUS-NIRS results acquired simultaneously in the same coronary lesion. We retrospectively enrolled 66 patients in whom 66 coronary lesions were assessed by NIRS-IVUS and QFR. Lesions were divided into two groups based on QFR results as QFR-positive group (QFR ≤ 0.8) or QFR-negative group (QFR > 0.8). Based on ROC curve analysis, the best cut-off values of minimal lumen area (MLA), minimal lumen diameter (MLD) and percent diameter stenosis for predicting QFR ≤ 80 were 2.4 (AUC 0.733, 95%CI 0.61, 0.834), 1.6 (AUC 0.768, 95%CI 0.634, 0.872) and 59.5 (AUC 0.918, 95%CI 0.824, 0.971), respectively. In QFR-positive lesions, the maxLCBI_4mm was significantly higher than in QFR-negative lesions (450.12 ± 251.0 vs. 329.47 ± 191.14, p = 0.046). The major finding of the present study is that values of IVUS-MLA, IVUS-MLD and percent diameter stenosis show a good efficiency in predicting QFR ≤ 0.80. Moreover, QFR-positive lesions are characterized by higher maxLCBI_4mm as compared to the QFR-negative group.

Contrast medium Pd/Pa ratio in comparison to fractional flow reserve, quantitative flow ratio and instantaneous wave-free ratio for evaluation of intermediate coronary lesions

INTRODUCTION

Contrast medium Pd/Pa ratio (cFFR) was introduced as an alternative to fractional flow reserve (FFR).

AIM

To assess the accuracy of cFFR in predicting of FFR, quantitative flow ratio (QFR) and instantaneous wave-free ratio (iFR).

MATERIAL AND METHODS

Resting Pd/Pa, cFFR, FFR, QFR, and iFR were measured in 110 intermediate coronary lesions. cFFR was obtained after intracoronary injection of contrast medium. FFR was measured after the intravenous administration of adenosine. QFR was derived from fixed empiric hyperemic flow velocity based on coronary angiography. iFR was calculated by measuring the resting pressure gradient across a coronary lesion during diastole.

RESULTS

Forty-four patients with 110 intermediate coronary lesions were enrolled. Mean baseline Pd/Pa was 0.93 ±0.05. Mean cFFR value was similar to FFR value (0.83 ±0.09 vs. 0.81 ±0.09; p = 0.13) and QFR (0.81 ±0.1; p = 0.69) and iFR (0.90 ±0.07; p = 0.1). A total of 46 vessels (41.8%) had FFR ≤ 0.80, 50 (45.5%) vessels had cFFR ≤ 0.83, 44 (40.0%) vessels had QFR ≤ 0.80, and 38 (34.5%) vessels had iFR ≤ 0.89. An excellent agreement between cFFR and resting Pd/Pa, FFR, QFR, and iFR was confirmed (intraclass correlation coefficients of 0.83, 0.99, 0.98, and 0.88, respectively). The optimal cutoff value of cFFR was 0.83 for prediction of FFR ≤ 0.80 with sensitivity, specificity, and accuracy of 96.9%, 97.8%, and 97.3%, respectively. 100% sensitivity was observed for a cutoff value of 0.82 and 100% specificity for a cutoff value of 0.84; AUC = 0.998 (0.995-1.00); p < 0.001.

CONCLUSIONS

Contrast medium Pd/Pa ratio seems to be accurate in predicting the functional significance of borderline coronary lesions assessed with FFR, iFR, and QFR.

Meta-Analysis of Diagnostic Performance of Contrast-Fractional Flow Reserve versus Quantitative Flow Ratio for Functional Assessment of Coronary Stenoses

Background. Use of the fractional flow reserve (FFR) technique is recommended to evaluate coronary stenosis severity and guide revascularization. However, its high cost, time to administer, and the side effects of adenosine reduce its clinical utility. Two novel adenosine-free indices, contrast-FFR (cFFR) and quantitative flow ratio (QFR), can simplify the functional evaluation of coronary stenosis. This study aimed to analyze the diagnostic performance of cFFR and QFR using FFR as a reference index. Methods. We conducted a systematic review and meta-analysis of observational studies in which cFFR or QFR was compared to FFR. A bivariate model was applied to pool diagnostic parameters. Cochran’s Q test and the I2 index were used to assess heterogeneity and identify the potential source of heterogeneity by metaregression and sensitivity analysis. Results. Overall, 2220 and 3000 coronary lesions from 20 studies were evaluated by cFFR and QFR, respectively. The pooled sensitivity and specificity were 0.87 (95% CI: 0.81, 0.91) and 0.92 (95% CI: 0.88, 0.94) for cFFR and 0.87 (95% CI: 0.82, 0.91) and 0.91 (95% CI: 0.87, 0.93) for QFR, respectively. No statistical significance of sensitivity and specificity for cFFR and QFR were observed in the bivariate analysis (P=0.8406 and 0.4397, resp.). The area under summary receiver-operating curve of cFFR and QFR was 0.95 (95% CI: 0.93, 0.97) for cFFR and 0.95 (95% CI: 0.93, 0.97). Conclusion. Both cFFR and QFR have good diagnostic performance in detecting functional severity of coronary arteries and showed similar diagnostic parameters.