Residual Quantitative Flow Ratio to Estimate Post‐Percutaneous Coronary Intervention Fractional Flow Reserve

Figures

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  Figure 1. Case example of residual QFR analysis. (a-b) Two end-diastolic frames of ICA in a patient with a proximal LAD lesion (FFR: 0.77). The stenosis was angiographically and functionally (post-PCI FFR: 0.96) successfully revascularized (c-d). During the QFR analysis, vessel contours were automatically detected on the two end-diastolic frames and manually corrected if needed (e). A 3D model of the coronary was reconstructed based on the vessels contours and lesions are presented as a drop in vessel diameter and QFR (g-f). The proximal and distal markers of the lesion in the QFR analysis were matched with the treated location during PCI to allow virtual removal of the lesion (c, f-g). Residual QFR was calculated by adding the delta QFR of the lesion to the vessel QFR (g). FFR: fractional flow reserve, ICA: invasive coronary angiography, LAD: left anterior descending artery, PCI: percutaneous coronary intervention, and QFR: quantitative flow ratio.

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  Figure 2. Flowchart of patients and vessels that were included and excluded. AUC, area under receiver operating characteristic curve; FFR, fractional flow reserve; PCI, percutaneous coronary intervention; QFR, quantitative flow ratio; ICA, invasive coronary angiography.

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  Figure 3. Correlation and agreement between QFR and pre-PCI FFR and residual QFR and post-PCI FFR. Scatterplots with corresponding correlation coefficients and Bland–Altman plots with ICCs demonstrating the correlation and level of agreement between QFR and pre-PCI FFR and residual QFR and post-PCI FFR. FFR, fractional flow reserve; PCI, percutaneous coronary intervention; QFR, quantitative flow ratio; CI, confidence interval; ICC, intraclass correlation coefficient; SD, standard deviation.

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  Figure 4. Diagnostic performance of residual QFR for detecting a suboptimal PCI result. ROC curve with AUC demonstrating the performance of residual QFR to predict a suboptimal PCI result defined by post-PCI FFR < 0.90. AUC, area under receiver operating characteristics curve; FFR, fractional flow reserve; PCI, percutaneous coronary intervention; QFR, quantitative flow ratio; CI, confidence interval; ROC, receiver operator characteristics.

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  Figure 5. Case examples of true positive and true negative residual QFR results. Case 1 demonstrates a case of a successfully treated proximal LAD lesion with a suboptimal post-PCI FFR (1a-b). Residual QFR estimated a post-PCI FFR of 0.85 (1c–e). The suboptimal result was caused by a pressure drop due to an additional lesion in the mid-LAD (1d). In case 2, residual QFR was 0.86 and FFR after treating the proximal LAD lesion was 0.80 (2a–e). QFR analyses revealed diffuse disease without a focal pressure drop to be the potential cause of the suboptimal result (2D). The last case demonstrates a case of a true negative result; the lesion in the proximal LAD was successfully treated, and there were no additional lesions or diffuse disease which led to a concordant residual QFR and post-PCI FFR ≥ 0.90 (3a–e). FFR, fractional flow reserve; PCI, percutaneous coronary intervention; QFR, quantitative flow ratio; LAD, left anterior descending artery.

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  Figure 6. Case examples of false negative and false positive residual QFR results. Case 1 displays a false negative residual QFR result. Post-PCI FFR remained suboptimal after a successful intervention in proximal to mid LAD (1a-b). Residual QFR estimated a post-PCI FFR of 0.98, and there was no significant pressure drop observed beside that of the treated lesion (1c–e). Contrary, case 2 shows a satisfactory PCI result of the RCA (2a-b). However, residual QFR predicted a suboptimal PCI result based on the presence of additional stenosis that proved not to be functionally relevant (2c–e). FFR, fractional flow reserve; PCI, percutaneous coronary intervention; QFR, quantitative flow ratio; LAD, left anterior descending artery; RCA, right coronary artery.