Recently approved by the FDA for use in the United States, the first ever fully bioresorbable heart stent is poised to bring significant changes to the way we treat coronary artery disease. Read on for more details on the history, functioning, and implications of this innovative new medical technology.
What does a heart stent do?
Heart stents are essentially a kind of scaffolding used to prop open arteries in patients with coronary artery disease.
Responsible for about 370,000 deaths in the United States each year, coronary heart disease develops when cholesterol deposits build up inside the coronary arteries, narrowing the passage along which blood can move and therefore decreasing overall blood flow to the heart. This leads to symptoms such as chest pain, fatigue, and shortness of breath; if a clot forms and completely blocks an artery, a heart attack results.
Stents help treat this problem by holding the artery open and preventing it from narrowing or collapsing back in on itself. A traditional stent is a tiny tube made of wire mesh; it is inserted into the narrowed spot in a patient’s artery during a procedure called angioplasty.
What’s the difference between a traditional stent and a bioresorbable stent?
The most important differences between traditional and bioresorbable, or dissolving, stents concerns what they are made of and how long they last.
Traditional stents are made of metal, and once they are inserted into a patient’s artery, they remain there permanently. While metal stents have been in widespread use since they were first introduced in the early 1990s, they are not without a number of disadvantages. Because they are permanently embedded, stents cause a patient’s artery motion to be limited for the rest of their life, and the risk of scar tissue formation within the stent itself could lead to a future renarrowing of the arteries. Furthermore, while stents have been shown to relieve chest pain, they have not been proven to prolong life more effectively than simply staying on heart medication.
Bioresorbable stents, on the other hand, eliminate the problem of permanence because they are made of a polymer similar to those used to make other absorbable devices, like sutures. Absorb, the patented dissolving stent made by Abbott that recently received FDA approval, breaks down over time into water and carbon dioxide; within three years of implantation, once artery healing is complete, the stent is fully reabsorbed. Because no metal is involved, the stented artery is able to pulse and flex naturally and the potential for future blockages is reduced. Because the stent is not permanent, it is easier for the patient to access follow-up procedures and other treatment options in the future should the need arise.
What are some implications of bioresorbable stent use?
While bioresorbable stents like Absorb hold significant promise for the future treatment of coronary artery disease, there are still a number of important considerations to be aware of.
For example, Absorb has thicker support struts than a traditional metal stent; because these struts protrude more into the artery and cover a larger proportion of the vessel wall, different implantation techniques are required to properly insert Absorb. Experts are concerned that a new, more intensive implantation procedure could be more time-consuming and costly. Furthermore, the added bulkiness of absorbable stents means that they are not a suitable choice for patients with very small arteries, who are among those more at risk for clot formation.
In terms of cost implications, although the upfront costs of using a resorbable stent may be higher, they will likely be offset by future savings as repeat procedures and other treatments related to the use of metal stents will not be needed.
A history of heart stents
The creation and approval of Absorb is the latest advance in a process of stent development that has been going on for more than 40 years in an effort to help patients with advanced coronary artery disease avoid open-heart surgery. Here are some of the key dates in the history of heart stents:
1977—The first balloon angioplasty was performed by cardiologist Andreas Gruentzig. In this procedure—essentially like a contemporary angioplasty but without the stent—a tiny balloon was inserted into an artery blockage and inflated to open the artery and restore blood flow. However, because of the balloon’s instability, balloon angioplasty came with significant limitations. Around 10% of vessels closed or recoiled within 24 hours of the procedure, and within six months, nearly half of vessels were closed.
1994—The first metal stent was introduced in the US by Johnson & Johnson. The metal stent eliminated the problem of vessels recoiling or closing, but introduced new complications in the form of scar tissue formation, which occurred in 30-40% of cases and required repeat procedures.
2003—Drug-coated stents were introduced by Johnson & Johnson. These metal stents elute medication that helps prevent the formation of scar tissue, but reclogging can begin one year after implantation.
2016—The first bioresorbable stent is approved by the FDA.