Flow patterns through vascular graft models with and without cuffs

Figures

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  Fig 1. Sketch of a model vascular graft along with the experimental setup. Flow is right-to-left. The model shown is configured for DPIV measurements; the laser sheet is shown entering from the top of the page. The digital camera captures images of light scattering from small neutrally-buoyant particles seeded in the flow.

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  Fig 2. Sketches of the bypass graft models. (a) Side view and (b) bottom view. Dashed lines indicate the straight end-to-side model and solid lines indicate the contoured end-to-side model. Flow is right-to-left with the native vessel aligned horizontally across the field-of-view.

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  Fig 3. Pulsatile flow waveforms of interest corresponding to rest and excitation states.

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  Fig 4. Direct comparison of the straight end-to-side (a-l) and the contoured end-to-side (a’-l’) grafts over one rest cardiac cycle. Time between successive vector fields is 70 msec. Contour legend and reference vector is shown in (a).

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  Fig 5. Close up of Fig 4D and 4D’. Separation, recirculation and stagnation are clearly visible in the straight end-to-side (a) while similar phenomena are weaker or nonexistent in the contoured end-to-side (b).

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  Fig 6. Comparison of back flow unsteadiness occurring during diastole for the rest case. Flow in the straight end-to-side rolls up into a strong vortex. Note that there is some flow through the stagnation region (indicated in Fig 5A), but this is in the counter-flow direction.

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  Fig 7. Side-by-side comparison of the straight and contoured end-to-side grafts near peak systole with an excitation cardiac cycle. Note the stagnation region is larger and more stable than in the rest case.

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  Fig 8. DPIV vector field for the straight end-to-side graft shortly after diastole for the excitation case. Observe that the stagnation region highlighted in Fig 7A remains throughout the cycle. Also note the high shear in the toe region even for low flow rates during diastole.

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  Fig 9. Side-by-side comparison of the two grafts for a rest cardiac cycle and 10% retrograde flow. Time between successive vector fields is 140 msec or ~17% of one cardiac cycle.

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  Fig 10. Single DPIV vector fields showing bottom views of flow through the straight end-to-side (a) and contoured end-to-side (b). The measurement plane is centered on the mid-plane of the native vessel. Images were shown at diastole.

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  Fig 11. DPIV vector fields for an excitation cardiac cycle and 10% retrograde flow for the straight end-to-side (a, b) and contoured end-to-side (c, d) grafts. The time points shown are at peak systole (a, c) and diastole (b,d).

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  Fig 12. Schematic drawing of a graft model highlighting key flow features through the anastomosis at systole.