Mechanically Optimized Bypass Grafts for Treating Patients with Peripheral Artery Disease in the Lower Limb

Courtney Keiser Author

04/06/2021 Added

53 Plays

Description

Courtney's graduate research work developing mechanically optimized vascular bypass grafts for treating patients with PAD

Searchable Transcript

Search:

[00:00:00.780]Hi,
[00:00:01.530]my name is Courtney Keiser and I'm a fifth year PhD student in mechanical and
[00:00:05.190]materials engineering. Today.
[00:00:06.930]I'm going to be giving you a brief overview of my research,
[00:00:09.360]developing mechanically optimized,
[00:00:11.130]vascular bypass graphs for treating patients with peripheral artery disease.
[00:00:15.780]Peripheral artery disease often refers to an obstruction of the femoral
[00:00:19.110]popliteal artery,
[00:00:20.070]which is your main artery in your leg that decreases blood flow to the lower
[00:00:23.430]limbs and affects 8.5 million adult Americans,
[00:00:27.210]which is close to roughly five times.
[00:00:28.860]The population of Nebraska total annual costs for hospitalizations for patients
[00:00:33.840]with pad is an excess of 21 billion per year.
[00:00:37.560]This high cost is attributed to a high operation and high intervention failure
[00:00:41.430]rate, which leads to poor treatment outcomes and a need for reintervention.
[00:00:45.810]The images on the right showed the femoropopliteal artery and the two sites
[00:00:49.740]of PAD occlusion that are clinically seen the most are above and below the knee.
[00:00:55.500]The treatment typically involves surgically implanted conduits called bypass
[00:00:59.400]graphs that redirect the blood flow around the occluded area.
[00:01:02.880]The image on the far right shows the greater saphenous vein being used,
[00:01:06.630]unfortunately, 20 to 45% of patients do not have this fan available.
[00:01:10.710]And its ability to stay open is very low within the first year.
[00:01:16.620]A synthetic graft is the next best solution,
[00:01:18.930]but they fail frequently with recent evidence suggesting that this is because
[00:01:22.470]they're high stiffness promotes kinking and tortuosity during limb flection.
[00:01:27.450]My research objective was to develop a reinforced bypass graft with resistance
[00:01:32.100]to kinking and tortuosity by optimizing the graphs mechanical properties to
[00:01:36.180]mimic young, healthy artery.
[00:01:37.890]The images on the LEFT are CT scans of living young and old subjects that
[00:01:42.390]demonstrates a loss of longitudinal tension in the femoral popliteal artery that
[00:01:46.680]prevents kinking and tortuosity during limb flection.
[00:01:50.190]The images on the right are a 2d angiogram and a 3d CT scan from
[00:01:54.750]patients treated with this stiff commercial PTFE bypass grafts.
[00:02:00.180]The black arrows are showing blood flow disturbances from where the graft is
[00:02:04.320]kinking and the red arrows show the graphs tortuosity these
[00:02:09.210]clinical results demonstrate a need to make grafts that are resistant to
[00:02:14.070]kinking and tortuosity.
[00:02:17.370]Bypass.
[00:02:17.850]Grafts were made by electro spinning technique that uses an electric field to
[00:02:21.600]draw out a charged polymer solution to create a non-woven elastomeric nanofiber fabric
[00:02:25.860]fiber fabric between the layers I worked on developing a polymer reinforcement
[00:02:30.030]material and a deposition technique that would allow for kink resistance and
[00:02:34.020]radial support mechanical properties were optimized by modulating the elastomer
[00:02:38.610]ratios,
[00:02:39.330]wall thickness reinforcement material in pattern and nanofiber orientation to
[00:02:43.140]match those of healthy human arteries.
[00:02:46.020]I used uniaxial tensile tests of human femoropopliteal arteries that were
[00:02:50.040]generously donated that were generously donated from live on Nebraska to guide
[00:02:54.900]the fabrication process here, I've created a database of,
[00:02:59.440]of longitudinal mechanical properties of human arteries from different age
[00:03:02.800]groups to understand the amount of force required to stretch the artery as you
[00:03:06.640]move from left to right, the age bracket increases.
[00:03:09.160]And one can see from the increased slope in the curves that with age or arteries
[00:03:12.970]are stiffening and requiring more force to stretch.
[00:03:17.080]The top left plot shows the force versus stretch characteristics of some of my
[00:03:21.400]better graft prototype. The top right plot shows a commercial.
[00:03:26.170]It shows a commercial reinforced bypass graft to notice in yellow,
[00:03:29.500]which is stiff and requires a lot of force to stretch.
[00:03:32.800]Then there are my bypass grafts that are red,
[00:03:35.230]orange and green that are slowly converging on being similar
[00:03:40.090]to a young, healthy artery, which is denoted in blue.
[00:03:44.080]The bottom of image.
[00:03:45.100]It shows some of my prototypes and their reinforcement patterns and the bottom
[00:03:48.550]right, demonstrates my reinforced grafts ability to stretch longitudinally,
[00:03:54.850]to test my grafts resistance to tortuosity. I designed in 3d printed,
[00:03:59.770]a simulated limb flection device on the far left a commercial bypass graft is
[00:04:04.690]mounted and show significant tortuosity when the hinge has been,
[00:04:08.290]the middle panel shows my bypass graft without any longitudinal tension that is
[00:04:12.790]inherent to the femoral popliteal artery.
[00:04:15.010]And you can see there's mild tortuosity on the far right panel is my bypass
[00:04:19.180]graft with 30% pre-stretch.
[00:04:22.480]And my graft is able to have minimal tortuosity compared to the middle and left.
[00:04:26.950]Panel.
[00:04:29.470]On the bottom image,
[00:04:30.850]you can see that my graft is able to resist kinking compared to the commercial
[00:04:34.180]graft to take these tests. One step further.
[00:04:38.200]I was able to test my grafts resistance to tortuosity in a perfused human
[00:04:42.730]cadaver model.
[00:04:45.100]Computerized tomography images were taken of the limbs in different
[00:04:50.080]postures to measure 3d deformations of the FPA with my bypass graft in a
[00:04:54.250]commercial PTFE graft. The results demonstrated that my graft,
[00:04:58.750]which is shown in green,
[00:05:00.520]was able to accommodate limb flection with minimal tortuosity compared to the
[00:05:04.030]standard supported PTFE graft, which is shown in purple.
[00:05:08.050]The red arrows are pointing to locations of graph tortuosity and actually
[00:05:11.290]coincide very well with what is clinically seen. So in conclusion,
[00:05:16.330]our results suggest bypass graphs with longitudinal compliance tuned to young,
[00:05:20.320]healthy human arteries,
[00:05:21.700]reduce kinking and tortuosity during limb flection and could potentially lead to
[00:05:25.510]better clinical performance for arterial repairs.
[00:05:28.540]And this might spark the development of a next generation vascular bypass graft
[00:05:32.980]current in future work involves compliance between human arteries and bypass
[00:05:37.240]grafts on a flow circuit that I designed in the bottom ripe cyto toxicity
[00:05:41.920]testing and future animal studies.
[00:05:46.090]I'd like to thank my advisor, Dr. Alexey Kamenskiy, my co-advisor Dr.
[00:05:49.750]Jason McTaggart and my mentor, Dr.
[00:05:51.880]Kaspar's Maleckis for all of their help and guidance throughout my research.
[00:05:55.210]And I'd also like to thank my UN MC collaborators, my UNL collaborators,
[00:05:59.200]and my UNL collaborators for all their help.

The screen size you are trying to search captions on is too small!

You can always jump over to MediaHub and check it out there.

Comments

0 Comments

Mechanically Optimized Bypass Grafts for Treating Patients with Peripheral Artery Disease in the Lower Limb

Description

Searchable Transcript

Comments icon comment

Related Channels

Comments