Model studies of the hemodynamics in abdominal aortic aneurysms and stenotic coronary arteries

Abdominal aortic aneurysms (AAAs) are an important health risk because they are largely asymptomatic until the onset of rupture which often leads to sudden death. Although many researchers have studied the hemodynamics of AAAs using numerical simulation, there are few experimental studies and few which explore the differences in physiologically realistic conditions for humans. The objective of this investigation was to characterize pulsatile flow through a range of AAA sizes for the physiologic conditions of resting and exercise. We used models of AAAs for several shapes and sizes emulating early AAA development through moderately large AAA growth. Our experimental and computational results for resting conditions in moderately sized AAAs agree quite well. Compared to axisymmetric AAAs, asymmetric AAAs show similar vortex formation but diminished vortex translation. We observe turbulent now under exercise conditions and laminar vortical flow under resting conditions in the moderately large AAA models. From video and still photography we observe ring vortex bursting into turbulence in moderately large AAAs under exercise conditions. This type of vortex bursting has not previously been described in the literature. Three distinct flow regimes are described for pulsatile flow through AAA models: (i) Attached flow over the entire cycle in small AAAs at resting conditions, (ii) Vortex formation and translation in moderate size AAAs at resting conditions, (iii) Vortex formation, translation and bursting into turbulence in moderate size AAAs under exercise condition.;Heart disease is the number one cause of death in the United States. Our objective was to characterize the hemodynamics of the coronary artery stenosis which may lead to heart attack. We used physiologically realistic flow models and studied restrictions which were concentric, eccentric and with three degrees of wall roughness. We acquired video and still photos. We found coronary artery flow produces recirculation zones distal to the constriction, and the length of the recirculation zone varies during the cardiac cycle. We see weak recirculation in all but the most constricted stenosis models, suggesting that thrombus formation is facilitated until the final stages of artery blockage. We observed no flow instabilities or transition to turbulence, and no turbulent flow.