Possible Early Generation of Physiological Helical Flow Could Benefit the Triflo Trileaflet Heart Valve Prosthesis Compared to Bileaflet Valves

Figures

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  Figure 1. (a) Adapted sketch from the schematic drawing by Kilner et al. [18] to illustrate the evolution of helical flow in the aortic arch; (b) hypothesis of the authors with early helical flow generated in the ventricular outlet tract, illustrated by an artistic schematic drawing of a streamtube entering the valve plane. The scene is shown for the case of interaction with an implanted bileaflet mechanical heart valves (MHV).

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  Figure 2. (a) Sketch of the pulse duplicator and (b) Flow profile in the systolic phase.

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  Figure 3. Tested heart-valve prostheses and their orientation within the phantom aorta. Left column: A tubular insert in form of an open orifice nozzle with circular cross-section and thin wall to cover the sinuses, forming a continuous, smooth tubular bend. Middle column: SJM Regent BMHV size 25 mm, with the leaflets in a fully open position (opening angle: 85°) and in the closed position (closed angle 25°). Right column: Triflo TMHV size 25 mm with the leaflets in the fully open position (opening angle 90°) and in the closed position (closed angle 40°). The solid arrow marks the centre orifice jet, and the dashed arrows mark the side orifice jets.

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  Figure 4. Details of the phantom aorta (including sinuses and brachiocephalic arteries) (DA = 25 mm, Ri = 18 mm, Ro = 43 mm) with additional inlet swirl generator module upstream of the aortic valve plane, (a) top view, (b) front view. The converging inlet nozzle had an initial diameter DN = 40 mm and length of 2DN, in which the swirl generator with an exit angle of 30° was inserted. For optical flow diagnostics, the transparent model was placed in a liquid container filled with the working fluid. This allows unobstructed view into the inner flow and velocity measurements using the HS-PIV method. The measurement plane can be arranged in the horizontal cross-section above the valve plane and in the vertical symmetry-plane of the bend.

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  Figure 5. Circular orifice flow with inlet swirl at peak systole observed in the pulse duplicator. Left: Pathlines at peak systole shown by multi-exposure images in the light-sheet crossing the centre plane; right: velocity field in the cross-section distal to the sinuses of Valsalva (SOV) indicating the vortex core (color levels indicate axial vorticity, the inner circle shows the diameter of the vortex core). The length of the reference vector indicates the peak inlet velocity (UP = 0.95 m/s).

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  Figure 6. Peak negative vorticity value in the vortex core at the cross-section distal to the SOV in the Pulse Duplicator compared to the 4D MRI flow data of von Spiczak et al. [14] in ROI 1 at a similar position. Note the early development of the vortex in the plane distal to the SOV.

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  Figure 7. HS-PIV visualization of the flow evolution in the centre plane of the phantom aorta for the Triflo valve with/without inlet swirl in the Pulse Duplicator: Color-coded contours of constant axial velocity (top) and axial velocity profiles in the centre plane. “S” indicates a separation point.

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  Figure 8. HS-PIV visualization of the contours of axial velocity magnitude (top) and axial velocity profiles in the centre plane during systole in the Pulse Duplicator for BMHV. “S” indicates a separation point.

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  Figure 9. Enlarged view of the velocity vectors in the left sinus for the TMHV without and with swirl (t/Tsys = 0.34) with radial inwards-directed flow supporting early valve closure (with swirl).

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  Figure 10. Cross-sectional flow field distal MHVs with contours of regions of constant angular velocity around a common centre of rotation. As a reference, the flow field for the open orifice is included at the left of the figure, too. The flow field is averaged over the peak systolic phase.