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Generally, the provisional approach of placing one stent in the main vessel (MV) is the preferred first-line treatment for most bifurcation lesions. However, the assessment of the side branch (SB) sometimes is difficult after MV stenting. Both Visual Estimation (VE) and Quantitative Coronary Angiography (QCA) are unreliable in assessing the functional severity of these lesions. The using of a pressure wire adds the extra cost; furthermore, it is sometimes difficult to advance a pressure wire to the distal of SB. In previous studies, we have validated that, based on first-pass distribution analysis and scaling laws, some hemodynamic indices such as coronary blood flow, Coronary Flow Reserve (CFR) and Fractional Flow Reserve (FFR) can be measured using only angiographic image data. The objective of this study was to evaluate the feasibility of physiologic assessment for SB lesions using these techniques of angiographic analysis.
A total of 24 patients with coronary bifurcation lesions underwent stenting with a provisional SB approach. VE, QCA, angiographic FFR (FFRa) and angiographic corrected FFR (cFFRa) were used to assess the SB ostial stenosis. In this study, we introduced the concept of cFFRa (we defined the normal vessels FFRa as 1 to correct the FFRa of the target vessel) for reducing the possible errors of our methodology. A pressure wire was placed into the SB to measure the FFR as a reference standard of functional significance. A stenosis was considered hemodynamically significant when the FFRa, cFFRa or FFR value was ≤ 0.80 and anatomically significant when the VE or QCA diameter stenosis was >50%. Correlations between VE/QCA/FFRa/cFFRa parameters and FFR were assessed by Spearman correlation analysis. Receiver-operating characteristic curve analysis was performed to assess the discriminatory power of the VE, QCA, FFRa and cFFRa parameters.
In 24 patients, 3 patients failed to SB access to measure the FFR values. Among 21 SB ostial stenoses, 16, 13, 11, 8 and 9 stenoses were suggested to have the functional significance according to the VE, QCA, FFRa, cFFRa and FFR assessment respectively. Correlation between FFR and VE (r=-0.29, p<0.01) /QCA(r=-0.42, p<0.01) was poor but significantly improved by FFRa (r=0.52, p<0.01)/cFFRa (r=0.71, p<0.01) by Spearman correlation analysis. The area under the receiver-operating characteristics curve for predicting FFR≤0.80 was significantly higher by cFFRa (0.83, 95% confidence interval: 0.61 to 0.82) compared with VE (0.54, 95% confidence interval: 0.49 to 0.72), QCA (0.66, 95% confidence interval: 0.56 to 0.74), and FFRa (0.70, 95% confidence interval: 0.60 to 0.79). Sensitivity and specificity for predicting ischemia-inducible bifurcation lesion (FFR≤ 0.8) were 72.7% and 38.0% for VE; 68.6% and 46.6% for QCA; 68.6% and 58.6% for FFRa; 62.6% and 72.6% for cFFRa respectively.
The angiographic analysis technique can be used to evaluate the SB ostial stenoses after Provisional Stenting Technique. cFFRa has the potential to be developed as a useful indicator to predict the functional significance of obstructive bifurcation stenoses.