The Wonderful World of Cardiac Stents

Before I started my nurse training I was a HCA for a Coronary Care Unit and was lucky enough to spend some time in the Cardiac Catheter Lab and attend some of the training sessions they provided for their nursing staff. Part of these sessions involved teaching around the wonderful world of stents. A recent documentary from the BBC about materials used in healthcare inspired me to learn a bit more about stents and write this post.

Patients that suffer from angina or a myocardial infarction typically have blockages or narrowing of the arteries supplying the heart. This is normally caused by atherosclerosis formation in these areas, preventing oxygenated blood from reaching the heart muscles. The first surgical intervention for this was the balloon angioplasty, where a balloon was inflated in the affected area, expanding the diameter of the artery (Gruntzig, 1978). However, this still had high rates of reoccurrence, leading to the invention of a metal scaffold called a stent (Puel et al., 1988). These metal stents were placed over the balloon and left in place once it was deflated. Things have come on a bit since then…

Bare Metal

The original form of stents, where it is simply a mental scaffolding that sits inside the narrowing of the artery, with no drugs being incorporated in its design. These displayed higher rates of restenosis and their use has been steadily decreasing since the introduction of DES. However, they do still have a place in the Cath lab, and can be used in patients who cannot adhere to the dual-antiplatelet therapy, require non-cardiac surgery soon after the stent placement or are at a high risk of bleeding (Colombo, Giannini and Briguori, 2017).

Drug Eluting Stents

In 1999, the first drug-eluting stent was implanted in a human with the hope of reducing these restenosis rates along with other associated complications. These stents are thinner and more flexible than their bare metal counterparts. They are covered in a drug that is designed to prevent restenosis, stopping any extra tissue growth from the artery around the edge or inside the stent (Nielsen et al., 2016). This drug is contained in a polymer coating on the stent, with different brands of stent releasing different drugs that work in similar ways – most commonly these are anti-thrombotic, anti-neoplastic or immunosuppressant effects. Research shows that these stents are associated with decreased incidence of adverse events and reduce the need for repeat balloon angioplasties (Feinberg et al., 2017).

Common DES Drugs Function
Paclitaxela Antimitotic agent that inhibits cell division
Sirolimus, everolimus, tacrolimus, zotarolimus Immunosuppressive agent
Dexamethasone Synthetic adrenocortical steroid that reduces inflammation

Bio-reabsorbable Stents

The baby of the stent family is the new reabsorbable stents. Not currently available in the UK except in trials, these stents are made of a polylactic mesh instead of metal and are absorbed over time. They still release drugs just like DES, but are still shown to have higher rates of stent thrombosis when compared (Cassese et al., 2016). Having a stent that is able to disappear after its period of drug-eluting could potentially reduce the risk of late stage restenosis and allow the vessel to regain its vasoactivity (O’Riordan, 2016).

Restenosis rates

POBA – 40%

BMS – 25%

DES – 5-10% depending on brand and generation

So what?

Like all other areas of healthcare, interventional cardiology is developing and utilising new devices and technologies at a fast rate. The field has come a long way since the use of balloon angioplasties and improvements will continue to decrease the risks and adverse events associated with the surgeries. As more improvements become available to cardiologists, patients that previously would have had to have more invasive treatments can be treated with percutaneous coronary interventions and stents. As a nurse, it is important to have at least a basic understanding of the use and function of stents as patients are more and more likely to have them; nurses need to understand the impact having these stents has on the patient’s life and the medications they may be taking.

References:

Thanks to Mike from Abbott Vascular for sending me loads of information.

Cassese, S. et al. (2016) ‘Everolimus-eluting bioresorbable vascular scaffolds versus everolimus-eluting metallic stents: a meta-analysis of randomised controlled trials’, The Lancet, 387(10018), pp. 537–544. doi: 10.1016/S0140-6736(15)00979-4.

Colombo, A., Giannini, F. and Briguori, C. (2017) ‘Should We Still Have Bare-Metal Stents Available in Our Catheterization Laboratory?’, Journal of the American College of Cardiology. Journal of the American College of Cardiology, 70(5), pp. 607–619. doi: 10.1016/j.jacc.2017.05.057.

Feinberg, J. et al. (2017) ‘Drug-eluting stents versus bare-metal stents for acute coronary syndrome’, Cochrane Database of Systematic Reviews, (8). doi: 10.1002/14651858.CD012481.pub2.

Gruntzig, A. (1978) ‘Transluminal dilatation of coronary-artery stenosis.’, Lancet, 1(8058), p. 263. Available at: http://www.ncbi.nlm.nih.gov/pubmed/74678.

NICE (2008) Drug-eluting stents for the treatment of coronary artery disease. NICE. Available at: https://www.nice.org.uk/guidance/ta152/chapter/3-The-technologies (Accessed: 21 November 2018).

Nielsen, E. E. et al. (2016) ‘Drug-eluting stents versus bare-metal stents for stable ischaemic heart disease’, Cochrane Database of Systematic Reviews, (12). doi: 10.1002/14651858.CD012480.

O’Riordan, M. (2016) Increased Early Risk of Stent Thrombosis With the Absorb Bioresorbable Scaffold, The Heart Beat. Available at: https://www.tctmd.com/news/increased-early-risk-stent-thrombosis-absorb-bioresorbable-scaffold?id=133501 (Accessed: 25 November 2018).

Poder, T. G. et al. (2017) ‘Percutaneous coronary intervention with second-generation drug-eluting stent versus bare-metal stent: Systematic review and cost-benefit analysis’, PLoS ONE, 12(5). doi: 10.1371/journal.pone.0177476.

Puel, J. et al. (1988) ‘Early and late assessment of stenosis geometry after coronary arterial stenting.’, The American journal of cardiology, 61(8), pp. 546–53. Available at: http://www.ncbi.nlm.nih.gov/pubmed/2964192 (Accessed: 21 November 2018).

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