In this work we present a one-dimensional (1D) mathematical model of the coronary circulation and use it to study the effects of arrhythmias on coronary blood flow (CBF). Hydrodynamical models are rarely used to study arrhythmias’ effects on CBF. Our model accounts for action potential duration, which updates the length of systole depending on the heart rate. It also includes dependency of stroke volume on heart rate, which is based on clinical data. We apply the new methodology to the computational evaluation of CBF during interventricular asynchrony due to cardiac pacing and some types of arrhythmias including tachycardia, bradycardia, long QT syndrome and premature ventricular contraction (bigeminy, trigeminy, quadrigeminy). We find that CBF can be significantly affected by arrhythmias. CBF at rest (60 bpm) is 26% lower in LCA and 22% lower in RCA for long QT syndrome. During bigeminy, trigeminy and quadrigeminy, respectively, CBF decreases by 28%, 19% and 14% with respect to a healthy case.

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.

Haemodynamic indices are widely used in clinical practice when deciding on a particular type of treatment. Low quality of the computed tomography data and tachycardia complicate interpretation of the measured or simulated values. In this work, we present a novel approach for evaluating resistances in terminal coronary arteries. Using 14 measurements from 10 patients, we show that this algorithm retains the accuracy of 1D haemodynamic simulations in less detailed (truncated) geometric models of coronary networks. We also apply the variable systole fraction model to study the effect of elevated heart rate on the values of fractional flow reserve (FFR), coronary flow reserve (CFR) and instantaneous wave-free ratio (iFR). We conclude that tachycardia may produce both overestimation or underestimation of coronary stenosis significance.

Invasive measurement of coronary fractional flow reserve (FFR) routinely involves the use of a pressure guidewire that will induce hemodynamic changes, thereby causing the measured FFR to deviate from the intact in vivo one. However, computational models used for predicting FFR often ignore the encroachment of vascular lumen by guidewire, which may compromise the comparability of model predictions with in vivo measurements. In this study, a geometrical multiscale model was developed to quantify the influences of two types of pressure guidewire (i.e., pressure wire and pressure catheter) on coronary hemodynamics and FFR. Numerical experiments were conducted on 35 idealized and 10 realistic models of the left anterior descending artery (LAD). Obtained results revealed that inserting a pressure guidewire into the LAD augmented the viscous pressure loss across the stenosis segment, leading to a decrease in blood flow rate, increase in trans-stenosis pressure drop, and consequently decrease in FFR. The guidewire-induced decrease in FFR was affected mainly by vascular diameter, stenosis rate, the number of stenosis, and the diameter of guidewire. More importantly, the study demonstrated the existence of a linear relationship between guidewire-present FFRs and guidewire-absent (intact) FFRs despite the large variations in stenosis rate and vascular morpho-geometrical characteristics, which could be explained by a theoretical model. These findings may serve as theoretical references for explaining or correcting the discrepancies between FFRs predicted by guidewire-absent models and in vivo measurements or converting invasively measured FFRs into the intact ones to better assess the functional impact of coronary artery stenoses.

In this work, we consider blood flow in the coronary arteries during the abnormal heart rhythm conditions due to the cardiac pacing and pathological type of the tachycardia. We adapt the ID model of...