Flow induced deformation of vulnerable stenosis under pulsatile flow condition

Abstract

A portion of vulnerable stenosis can be deformed periodically under pulsatile blood-flow condition. The deformable stenosis consists of fibrous cap covering a lipid pool, which is analogous to a capsule containing oily liquid or soft gel. The deformation increases mechanical stress acting on the fibrous cap. The magnitude of the stress determines likelihood of rupture, which causes sudden cardiac death or stroke. Previous studies tried to measure the stress by using intravascular imaging or numerical simulation. However, the methods have limitations of invasiveness and long process time in calculating the stress, respectively. In this study, the main determinants for the fibrous cap deformation and the normal stress acting on the fibrous caps are experimentally examined using deformable stenosis models. Particle image velocimetry is employed to measure flow induced forces acting on the fibrous caps. The deformable stenosis models are deformed to increase geometrical slope when inlet flow rate is increased. Deformation extent and mean normal stress acting on the fibrous caps are proportional to the square of the inlet flow rate and inversely proportional to the fibrous cap thickness. The periodic deformation of stenotic shape induces fluctuations of jet angle at the throat of the stenosis. Temporal variation of the jet angle is inversely proportional to the fibrous cap thickness of the deformable stenosis models. The variations of the jet angle for rigid stenosis models are negligibly small. The present results reveal the potential use of flow rate and variation of jet angle to approximate normal stress on the fibrous caps and to distinguish deformable stenosis from rigid stenosis. The flow rate and the jet angle can be measured directly by using noninvasive imaging devices in hospital.