Flow induced stress on vulnerable stenosis in tandem stenosed vessels

The diagnosis of sudden cardiac death has progressed with understanding of the rupture of vulnerable stenosis. Fluid dynamic analyses focused on flow-induced deformation and resultant stress on a vulnerable stenosis due to the rupture occurring when stress exceeds its intrinsic strength. The vulnerable stenosis is often observed with another stenosis in a tandem arrangement in the same blood vessel. However, the effect of tandem arrangement on the stress acting on the vulnerable stenosis has not been studied. In this study, flow characteristics and resultant stress on the vulnerable stenosis in tandem arranged models were experimentally investigated under pulsatile flow conditions. Results show that the phase-averaged stress is suppressed when the vulnerable stenosis is serially arranged behind another stenosis compared with that for a single vulnerable stenosis. In particular, the stress is relatively small when the distance between the two stenoses is shorter than the recirculating length of the proximal stenosis. Vortices generated from the proximal stenosis vibrate the vulnerable stenosis with a higher frequency than the pulsating frequency of the flow, thus creating the fluctuating component of the stress. The stress fluctuation for tandem stenoses is higher than that for a single stenosis, although the magnitude of stress fluctuations is smaller than 10% of the phase-averaged stress. Kinetic energy (KE) of the phase-averaged flow in front of the vulnerable stenosis and KE fluctuations are strongly influenced by the tandem arrangement. These parameters are good indicators for assessing the phase-averaged and fluctuating component of the stress exerted on the vulnerable stenosis.