Abstract
Background: Calculation of fractional flow reserve (FFR) using computed tomography (CT)-based 3D anatomical models and computational fluid dynamics (CFD) has become a common method to non-invasively assess the functional severity of atherosclerotic narrowing in coronary arteries. We examined the impact of various inflow boundary conditions on computation of FFR to shed light on the requirements for inflow boundary conditions to ensure model representation. Methods: Three-dimensional anatomical models of coronary arteries for four patients with mild to severe stenosis were reconstructed from CT images. FFR and its commonly-used alternatives were derived using the models and CFD. A combination of four types of inflow boundary conditions (BC) was employed: pulsatile, steady, patient-specific and population average. Results: The maximum difference of FFR between pulsatile and steady inflow conditions was 0.02 (2.4%), approximately at a level similar to a reported uncertainty level of clinical FFR measurement (3–4%). The flow with steady BC appeared to represent well the diastolic phase of pulsatile flow, where FFR is measured. Though the difference between patient-specific and population average BCs affected the flow more, the maximum discrepancy of FFR was 0.07 (8.3%), despite the patient-specific inflow of one patient being nearly twice as the population average. Conclusions: In the patients investigated, the type of inflow boundary condition, especially flow pulsatility, does not have a significant impact on computed FFRs in narrowed coronary arteries.
Highlights
Coronary arteries supply the heart muscle with oxygenated blood; when these are obstructed or blocked, the myocardium begins to fail in a process known as ischaemia
The high correlation between the fractional flow reserve (FFR) values obtained using a pulsatile simulation and that of a steady-state simulation indicates that the use of simple steady flow condition may be acceptable
Across the range of coronary artery stenosis from healthy to significantly diseased, the discrepancy of FFR between the steady state and the pulsatile simulation is small. This remains true for diseased left anterior descending artery (LAD) and left circumflex artery (LCx) arteries, where the systolic–diastolic discrepancy of the flow is high due to its higher impact of intramyocardial pressure that inhibits relatively low level of systolic flow
Summary
Coronary arteries supply the heart muscle (myocardium) with oxygenated blood; when these are obstructed or blocked, the myocardium begins to fail in a process known as ischaemia. Coronary artery disease (CAD) or ischaemic heart disease is the leading cause of death globally, and accounts for. CAD is most commonly diagnosed invasively using X-ray coronary angiography where projection images of the arteries are taken and assessed visually by a physician to determine the percentage of the artery cross section that is obstructed. Anatomical constriction by itself does not necessarily represent the functional severity of the obstruction [4]. Calculation of fractional flow reserve (FFR) using computed tomography (CT)-based 3D anatomical models and computational fluid dynamics (CFD) has become a common method to non-invasively assess the functional severity of atherosclerotic narrowing in coronary arteries. We examined the impact of various inflow boundary conditions on computation of FFR to shed light on the requirements for inflow boundary conditions to ensure model representation
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