What materials are stents used for heart conditions made of?

Materials Used in Coronary Stents

Coronary stents are primarily made of metals including stainless steel, cobalt chromium alloys, platinum chromium alloys, and nickel-titanium alloys (nitinol), with newer generations featuring biodegradable polymers and drug-eluting coatings.

Types of Coronary Stent Materials

Bare Metal Stents (BMS)

• Bare metal stents are composed of either stainless steel or cobalt chromium alloys 1
• These stents provide mechanical support to prevent vessel recoil and abrupt closure after angioplasty 1
• BMS require dual antiplatelet therapy (DAPT) for at least 30 days after implantation due to thrombosis risk 1

Drug-Eluting Stents (DES)

• Current FDA-approved DES include sirolimus-eluting, paclitaxel-eluting, zotarolimus-eluting, and everolimus-eluting stents 1
• DES consist of three main components:
  • A metallic stent platform (typically cobalt chromium or platinum chromium) 1, 2
  • A polymer coating that controls drug release 3
  • An antiproliferative drug to prevent restenosis 1
• DES require longer DAPT (typically 12 months) compared to BMS 1

Evolution of Stent Materials

First-Generation DES

• Early DES used stainless steel platforms with permanent polymers 3
• These stents reduced restenosis but had concerns regarding delayed healing and late stent thrombosis 3

Contemporary DES

• Modern DES feature cobalt chromium or platinum chromium platforms 2
• These alloys allow for thinner struts while maintaining adequate radial strength 2
• Newer DES incorporate biodegradable polymers that dissolve after drug elution is complete 3

Specific Stent Materials and Properties

Stainless Steel

• Traditionally used in first-generation stents 4, 5
• Provides good structural support but requires thicker struts 5
• Higher thrombogenicity compared to newer materials 4

Cobalt Chromium Alloys

• Offers greater radial strength with thinner strut designs 2, 5
• Improved deliverability and flexibility compared to stainless steel 2
• Better biocompatibility and reduced thrombogenicity 4

Platinum Chromium Alloys

• Enhanced radiopacity (visibility under X-ray) 2
• Good mechanical properties with thin strut designs 2

Nitinol (Nickel-Titanium Alloy)

• Features shape memory and superelasticity 5
• Causes fewer artifacts on MRI compared to other stent materials 1
• Particularly useful in self-expanding stent designs 5

Magnesium Alloys

• Used in some biodegradable stent platforms 4, 5
• Lower thrombogenicity compared to stainless steel and cobalt chromium 4
• Eventually absorbed by the body, potentially reducing long-term complications 5

Clinical Implications of Stent Materials

• Stent material affects key performance characteristics:

  • Deliverability and trackability in tortuous vessels 2
  • Radial strength to prevent vessel recoil 2
  • Thrombogenicity and risk of stent thrombosis 4
  • Visibility under imaging 1

• Ultrathin-strut cobalt chromium or platinum chromium DES are becoming the standard of care due to improved clinical outcomes 2

• The choice of stent material should consider:

  • Lesion complexity and calcification (requiring greater radial strength) 2
  • Risk of bleeding (affecting duration of DAPT) 1
  • Need for future MRI imaging (nitinol causes fewer artifacts) 1

Important Considerations for Specific Patient Scenarios

• For patients with high bleeding risk or anticipated surgeries within 12 months:

  • BMS may be preferred over DES due to shorter required DAPT duration 1

• For patients at high risk of restenosis:

  • DES are preferred over BMS to reduce repeat revascularization 1

• For patients unable to comply with extended DAPT:

  • DES should be avoided 1