Torsional Characterization of Braided Flow Diverter Stents : A New Method to Evaluate Twisting Phenomenon

Recanalization of a chronic occlusion flow-diverter device in a patient with a paraclinoid giant aneurysm recurrence. Clinical observation

Paraclinoid internal carotid artery (ICA) aneurysms are associated with a high mortality rate, which gradually increases without intervention. Surgical clipping or coiling of large aneurysms with inadequate neck and adductor artery expansion will not guarantee a successful outcome. Carotid surgical trapping or endovascular occlusion of the adductor artery can help to isolate the aneurysm from circulation, but it comes at the expense of sacrificing a major blood vessel responsible for significant cerebral perfusion. Currently, a technique has been developed to redirect blood flow and stimulate gradual thrombosis in the aneurysm cavity to reduce pressure on its walls. However, in cases of recurrent aneurysm and stent thrombosis in these patients, it is necessary to consider destructive surgery. The 65-year-old patient, who had a history of migraine, was diagnosed with a large aneurysm. He was initially treated with the Pipeline Flex stent from Medtronic, but after 5 months, he experienced 2 transient ischemic attacks. Subsequent CT scans revealed no signs of brain damage, but a brain CTA revealed the recurrence of an internal carotid artery paraclinoid aneurysm with the occlusion of the pipeline device and contrast flowing parallel to the aneurysm wall. This case is an example of successful recanalization of an occluded flow diverter device in a patient with recurrent internal carotid aneurysm.

A realistic way to investigate the design, and mechanical properties of flow diverter stents

PURPOSE

Braided flow diverters (FD) are highly sophisticated, delicate, and intricate mechanical devices used to treat intracranial aneurysms. Testing such devices in vitro, however, remains an unsolved challenge. Here, we evaluate methods to measure flow, design and mechanical properties in vitro.

METHODS

Flow properties, cell porosity, pore density, and cell area were evaluated under geometrically realistic conditions by placing FDs in patient-derived, 3D-printed models of human vasculature. 4D flow MRI was used to measure fluid dynamics. Laser microscopy was used to measure the design properties of the FDs. New methods were developed to investigate the bending, circumferential, and longitudinal radial force of the FDs continuously over varying diameters.

RESULTS

The placement and flow properties of the FD in the vasculature models were successfully measured by MRI, although artifacts occurred. Likewise, the porosity, pore density, and cell area were successfully measured inside of the models using a laser microscope. The newly developed mechanical methods allowed to measure the indicated forces - to our knowledge for the first time - continuously.

CONCLUSION

Modern and specifically tailored techniques, some of which were presented here for the first time, allow detailed insights into the flow, design, and mechanical properties of braided flow diverter stents.