Still a future for the bare metal stent?

Design and characterization of a novel nickel-free cobalt-base alloy for intravascular stents

Co-Cr-W-Ni alloy (L605) with high tensile strength is used in coronary stents. The thickness of individual strut of the stent is reduced which can decrease the stent restenosis rate. However, about 10% Ni element content in L605 is found to cause allergic reactions and pulmonary embolism, similar to the traditional 316L stainless steel. In this study, a novel nickel-free cobalt-base alloy Co-20Cr-12Fe-18Mn-2Mo-4W-N (wt%) was designed and fabricated in order to efficiently avoid the potential hazards of Ni element. Fe and Mn, essential elements of human body, were added in the alloy to substitute part of Co element. In comparison to L605 alloy, the tensile strength of the new alloy was higher than 1000MPa while elongation was above 55%. The pitting potential of the new alloy was measured close to 1000mV, also higher than that of L605 alloy. CCK-8 test indicated that the cytotoxicity of the new alloy is grade 1, reflecting that Co-20Cr-12Fe-18Mn-2Mo-4W-N alloy has no cytotoxic effects. There was no significant difference in the apoptosis rates between Co-20Cr-12Fe-18Mn-2Mo-4W-N and L605 alloy. The newly developed cobalt-base alloy showed excellent mechanical, corrosion resistance and biological properties, which could make it a desirable material for future clinical investigations.

A new way to reduce flow disturbance in endovascular stents: a numerical study

Traditional commercial stents are made of wires with square or semi-circular cross-sections that lead to flow disturbance, which plays an important role in the initiation and progression of restenosis. A new stent with streamlined cross-sectional wires was proposed and researched numerically for its hemodynamic performance. Simplified models of stents with square, semi-circular, or streamlined cross-sectional wires were constructed numerically. Blood flows in the three models were simulated using computational fluid dynamics methods, and compared in terms of flow pattern, wall shear stress (WSS), and oscillating shear index (OSI). The results showed that when compared with the two traditional stents, the new stent with streamlined cross-sectional wires induced almost no flow disturbance, significantly enhanced WSS, and reduced the value of OSI within the stent. The present preliminary study indicates that the optimization of the cross-sectional shape of stent wires ought to be considered in the structural design for endovascular stents.

The clinical presentation of restenosis after bare metal stent implantation: behind a facade of benignity

Contrary to common belief, bare metal in-stent restenosis (ISR) seems to be not a benign clinical entity. Thus,we believed that continued efforts are warranted to prevent bare metal ISR, including aggressive use of drug-eluting stent (DES) to decrease the incidence of acute coronary syndromes. However, despite improved outcomes with DES, bare metal stent (BMS) will continue to play a role for both clinical and economic reasons and we feel that there is still a future for BMS.