Experimental fluid dynamics of aortic stenosis in a model of the human aorta.

Aortic stenosis has been modelled in an in vitro, pulsatile mock circulatory system (MCS) using a porcine valvular prosthesis, and studied with a laser Doppler anemometer (LDA). The MCS incorporated an acrylic model of the human aorta made from a cadaveric casting in situ. A Carpentier-Edwards aortic valve prosthesis was placed in the MCS after being rendered stenotic by suturing of the valve cusps. Flow velocity profiles across the lumen of the aorta in the presence of aortic stenosis were determined using LDA at two preselected sites in the ascending aorta, and at one preselected site in the brachiocephalic artery. Results indicate that a strong systolic jet bordered by transient vortices with intensely reversed flows is produced distal to severely stenotic aortic valves, becoming less intense with a lesser degree of stenosis. Peak fluid velocities in the systolic jet were determined by LDA at distances of 2.6 and 5.6 cm from the valve inlet for a mean flow rate of 5.2 l min-1. Peak systolic pressure gradients and peak turbulent axial stresses were also determined and found to increase dramatically with stenosis. Furthermore, increasing degrees of stenosis also resulted in more severely disturbed flows in the brachiocephalic artery. Peak fluid velocities and their associated turbulent axial stresses in the systolic jets produced by aortic valvular stenosis are remarkably sensitive to even small changes in the calculated valve orifice areas, and can therefore be very useful in assessing the severity and progression of valvular disease. In addition, increasing degrees of aortic stenosis cause more turbulence to be transported into the brachiocephalic artery.