Do cardiac stents contain nickel?

From the Guidelines

Yes, many cardiac stents contain nickel as a component of the metal alloys used in their construction, with nitinol stents typically containing about 55% nickel and stainless steel stents containing 8-12% nickel. The most commonly used materials for stents include stainless steel, cobalt-chromium alloys, and nitinol (a nickel-titanium alloy), all of which contain varying amounts of nickel 1. This is clinically relevant because patients with nickel allergies may experience hypersensitivity reactions to these stents, potentially leading to in-stent restenosis or other complications.

Some key points to consider:

• Nitinol stents are made from a nickel-titanium alloy and contain a significant amount of nickel, which can be a concern for patients with nickel allergies 1.
• Stainless steel stents may also contain nickel, although at lower concentrations than nitinol stents 1.
• The presence of nickel in stents allows for beneficial properties like shape memory and superelasticity in nitinol stents, which helps them conform to vessel anatomy during deployment.
• For patients with known nickel allergies, alternative stent materials such as platinum-chromium alloys or gold-coated stents may be considered, though these options may have different performance characteristics 1.
• Physicians should take a careful allergy history before stent placement, especially in patients with a history of metal allergies or reactions to jewelry.

In terms of the types of stents available, the evidence suggests that:

• Bare-metal stents (BMS) are composed of either stainless steel or cobalt chromium alloys 1.
• Drug-eluting stents (DES) vary according to stent scaffold material and design, drug content, and the polymer used for drug elution, but several common clinical features are present, including a reduced need for repeat revascularization and no increase in death or MI compared with BMS at 4 years’ follow-up 1.

From the Research

Presence of Nickel in Cardiac Stents

• Most cardiac stents are made of stainless steel, which contains nickel, as well as other metals like chromate and molybdenum 2, 3.
• The use of nickel in cardiac stents has raised concerns about potential allergic reactions and inflammation, which could contribute to in-stent restenosis 2, 3, 4.
• Studies have investigated the relationship between nickel allergy and in-stent restenosis, with some finding no significant difference in the prevalence of metal allergy between patients with patent stents and those with in-stent restenosis 2, 3.
• Other research has focused on the development of nickel-free stainless steel stents, which have been shown to reduce neointima formation and inflammation in animal models 5.

Nickel and Inflammation

• Nickel ions and NiTi nanoparticles have been found to induce pro-inflammatory and pro-angiogenic cytokine/chemokine expression in human endothelial and monocyte cell lines in vitro 6.
• The intracellular uptake of Ni2+ has been correlated with the generation of reactive oxygen species, which can contribute to inflammation and angiogenesis 6.
• In vivo studies have used angioreactors to examine the angiogenic potential of nickel and NiTi nanoparticles, with results showing that NiTi NP are markedly angiogenic, while Ni2+ is less so 6.

Clinical Implications

• The presence of nickel in cardiac stents has raised concerns about potential adverse reactions, particularly in patients with a history of metal allergy 4.
• However, studies have found that a history of metal allergy is not associated with adverse early or late outcomes after stent implantation 4.
• Further research is needed to fully understand the effects of nickel on neointima formation and inflammation after stent implantation, and to develop new stent materials that minimize these risks 5.