Background: Until recently, Russia did not utilize noninvasive fractional flow reserve (FFR) assessment. We developed an automated algorithm for noninvasive assessment of FFR based on a one-dimensional (1D) mathematical modeling. Objective: The research aims to evaluate the diagnostic accuracy of this algorithm. Methods: The study enrolled 80 patients: 16 of them underwent 64-slice computed tomography – included retrospectively, 64 – prospectively, with a 640-slice CT scan. Specialists processed CT images and evaluated noninvasive FFR. Ischemia was confirmed if FFR < 0.80 and disproved if FFR ≥ 0.80. The prospective group of patients was hospitalized for invasive FFR assessment as a reference standard. If ischemic, patients underwent stent implantation. In the retrospective group, patients already had invasive FFR values. Statistical analysis was performed using GraphPad Prism 8. We compared two methods using a Bland–Altman plot and per-vessel ROC curve analysis. Considering the abnormality of distribution by the Kolmogorov-Smirnov test, we have used Spearman’s rank correlation coefficient. Results: During data processing, three patients of the retrospective and 46 patients of the prospective group were excluded. The sensitivity of our method was 66.67% (95% CI: 46.71–82.03); the specificity was 78.95% (95% CI: 56.67–91.49), p = 0.0052, in the per-vessel analysis. In per-patient analysis, the sensitivity was 69.57% (95% CI: 49.13–84.40); the specificity was 87.50% (95% CI: 52.91–99.36), p = 0.0109. The area under the ROC curve in the per-vessel analysis was 77.52% (95% CI: 66.97–88.08), p < 0.0001. Conclusion: The obtained indices of sensitivity, specificity, PPV, and NPV are, in general, comparable to those in other studies. Moreover, the noninvasive values of FFR yielded a high correlation coefficient with the invasive values. However, the AUC was not high enough, 77.52 (95% CI: 66.97–88.08), p < 0.0001. The discrepancy is probably attributed to the initial data heterogeneity and low statistical power.

We consider algorithms of 3D reconstruction for the internal surface of cardiac vessels. The precise reconstruction of vessel geometry is necessary for the creating a hydrodynamic model of blood supply for the heart and computing various parameters of blood flow. To compute a triangulation of blood vessel walls, we use the combination of two methods. At the first stage we apply the 3D seeded region growing algorithm to reconstruct a set of voxels inside vessels. At the second stage we use the isosurface reconstruction algorithm based on the tessellation of 3D space into small tetrahedral cells. We use the tetrahedral mesh, which was proposed in the works of S. Chan, E. Purisima (1998), and V. Skala (2000). Tetrahedra in this mesh are constructed on common faces of adjacent cubes in a cubic lattice, so it fits well with the voxel model. The mesh is constructed only in the neighborhood of the border of voxel set obtained at the first stage as the result of seeded region growing algorithms.

Patient: Male, 58Final Diagnosis: Coronary artery disease • silent myocardial ischemiaSymptoms: Silent myocardial ischemiaMedication: —Clinical Procedure: Noninvasive assessmant of fractional flow reserve • left descening artery revascularizationSpecialty: CardiologyObjective:Unusual setting of medical careBackground:Noninvasive assessment of the fractional flow reserve (FFR) in patients with coronary artery disease plays an important role in determining the need for revascularization. It is particularly relevant for patients with a borderline stenoses and painless myocardial ischemia. Our article describes the first clinical experience in the Russian Federation of using an automated method of noninvasive assessment of the fractional flow reserve (FFRct) with a one-dimensional (1-D) mathematical model in a patient with painless myocardial ischemia.Case Report:A 58-year-old male patient who underwent stent implantation in the left circumflex coronary artery (LCX) due to an acute non-ST-elevation posterior myocardial infarction had borderline stenoses of the left anterior descending artery (LAD). After stent implantation, there were no relapse angina symptoms on drug treatment, and according to our examination guideline for patients with borderline stenoses, a treadmill test was performed. The test was positive; therefore, FFR assessment was recommended, with coronary multi-slice CT being performed. The following results were obtained: FFRct LAD – 0.57; FFRct LCX – 0.88. An invasive assessment of FFR was also performed as a reference standard and revealed: FFR LAD – 0.6; FFR LCX – 0.88, and simultaneously a LAD percutaneous coronary intervention (PCI) was performed. Three months later, the patient underwent a stress test, which revealed no evidence of induced ischemia.Conclusions:Our method of noninvasive assessment of FFR has shown encouraging results, but we believe that larger-scale studies are needed to establish it as common clinical practice.

ель исследования. Тестирование (проверка) методики неинвазивного определения фракционного резерва кровотока (ФРК) на основании данных, полученных при проведении компьютерной томографической ангиографии (КТА) коронарных артерий. Результаты. Гидродинамический расчет кровотока в коронарной артерии позволил получить оценку ФРК с отклонением от инвазивно измеренных значений ФРК равным или меньшим 7%. Заключение. Продемонстрирован научный и клинический потенциал предложенной ранее методологии неинвазивного определения ФРК по результатам КТА для оценки функциональной значимости пограничных стенозов в коронарных артериях. Ключевые слова: фракционный резерв кровотока (ФРК), коронарные артерии, компьютерная томографическая ангиография (КТА), триангуляция поверхности, математическое моделирование.

analysis of diagnostic performance of coronary computed tomography angiography, computed tomography perfusion, and computed tomography-fractional flow reserve in functional myocardial ischemia assessment versus invasive fractional flow reserve.