Coronary artery disease
Validation of Functional State of Coronary Tandem Lesions Using Computational Flow Dynamics

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Functional lesion assessment for coronary tandem lesions and its clinical applications have not been thoroughly studied. The aim of this study was to test the hypothesis that the fractional flow reserve (FFR) gradient across an individual stenosis (ΔFFR) during pressure-wire pullback is a surrogate of the relative functional severity of each stenosis in coronary tandem lesions. For in vitro validation, computational flow dynamic modeling of coronary tandem lesion with various degree of stenosis was constructed. For clinical validation, a total of 52 patients (104 lesions) with coronary tandem lesions (2 stenoses along 1 coronary artery) were consecutively enrolled, and tailored stent procedures based on ΔFFR was performed, at first treating the lesion with large ΔFFR and then subsequently reassessing the FFR for the remaining lesion. The coronary stenosis was considered functionally significant and stenting was performed when the FFR of a lesion was ≤0.80. Using in vitro computational flow dynamic modeling, the lesion with the large ΔFFR of the coronary tandem lesion was indicated as the lesion with the greater degree of simulated diameter stenosis. In the clinical cohort, 28 patients (53.8%) had only single-lesion treatment, and stent implantation for 28 lesions (26.9%) was deferred according to the proposed strategy. During the 9-month follow-up period, only 1 repeat revascularization occurred among the deferred lesions. In conclusion, for the treatment of coronary tandem lesions, ΔFFR may be a useful index for prioritizing the treatment sequence and optimizing the stenting procedure. In this way, unnecessary stent implantation can be avoided, with the achievement of favorable functional and clinical outcomes.

Section snippets

Methods

To validate the study hypothesis, we developed CFD modeling for coronary tandem lesions. Figure 1 shows a schematic figure of a simulated coronary tandem lesion. We made a total of 147 combinations of the proximal (stenosis A, 30% to 90% diameter stenosis, increasing in increments of 10%) and distal (stenosis B, 30% to 90% diameter stenosis, increasing in increments of 10%) stenoses with distances of 10, 20, and 30 mm. Herein, percentage diameter stenosis created in the simulation is equivalent

Results

A total of 147 combinations of stenosis A and stenosis B were created. The change in FFR according to the differing stenosis severity of the other stenosis is shown in Figure 2. Figure 3 plots the relation between the differences in diameter stenosis of stenoses A and B and the differences in ΔFFR (A) and ΔFFR (B). Furthermore, the experimental results of Pijls et al2 were plotted for the external validation of our simulated results in Supplemental Figure 1. Figure 2 and Supplemental Figure 1

Discussion

In vitro assessment and CFD modeling in the present study demonstrated that ΔFFR corresponds to relative functional severity within functionally significant coronary tandem lesions. On the basis of this theory, treatment for an individual stenosis within a coronary tandem lesion could be prioritized by ΔFFR for treating patients with significant coronary tandem lesions, such as first treating the lesion with large ΔFFR and subsequently reassessing the FFR for the remaining lesion. As a result,

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This study was funded by Grant A102065 from the Korea Healthcare Technology R&D Project, Ministry of Health and Welfare, Republic of Korea, and by the Cardiovascular Research Foundation, Seoul, Korea.

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