This is about the Absorb Heart Stent, a new dissolving stent known as a Bio-absorbable Scaffold. Unlike traditional heart stents that remain for life, the Absorb heart stent dissolves over time to where it completely disappears. This has many advantages. In this article author, and cardiologist Mustafa Ahmed MD of Princeton Baptist Medical Center, Birmingham, Alabama explains the Absorb stent. Dr Ahmed was amongst the first to implant the commercially available Absorb stent in the US. Dr Ahmed implanted the stent in a patient of cardiologist Dr. Alain Bouchard with a Widowmaker heart blockage at Princeton Baptist Medical Center, Birmingham, Alabama. In this article we present information on the new stent, then we show the story of Mr. Richardson, a patient with the Widowmaker blockage treated with this Absorb dissolvable stent.

What is a Heart Stent?
Heart stents are used to treat blockages in the coronary arteries that supply the heart with blood. A total blockage in a coronary artery would lead to a heart attack, and if not treated rapidly can lead to death of heart muscle. A significant blockage of an artery, usually greater than 70%, can lead to symptoms such as chest pain, shortness of breath and heart muscle damage. Heart stents can be used to treat these heart blockages and open up the artery, relieving the blockage and restoring normal blood supply.

A heart stent is basically a small metal tube that is expanded inside the area of blockage. Once expanded it remains there and acts as a scaffold to keep the artery open. In the old days we used balloons to try and open the artery, but after the balloon was deflated the blockage would often recoil, meaning the chance of a successful procedure was not always good. With the development of heart stents, however, the scaffold from the stent prevented the recoil and meant the artery stayed open.

Problems with Traditional Heart Stents
Although the development of heart stents was a major breakthrough, the presence of these scaffolds within arteries was not entirely without problem. It’s important to remember that vessels are reactive in nature. They expand and constrict in response to various stimuli. This is prevented by metallic heart stents. Vessels themselves are always undergoing changes and the presence of heart stents can disrupt this process known as remodeling. If further work is required in other parts of vessels downstream to the heart stents, the heart stents can get in the way. Metallic heart stents often mean that patients are required to take life long blood thinning medication. These are just some of the problems associated with heart stents, and therefore it was very exciting when absorbable stents were developed.

The absorb stent is known as a bio-absorbable vascular scaffold (BVS) and is a huge breakthrough. The development of the Absorb stent meant that the stent could do its job, but then disappear over time leaving the vessel still open.

For those wishing to dig a little deeper, the science underlying the Absorb heart stent is fascinating. It is made of a bio-absorbable polymer, which is broken down over time. It also releases a drug that prevents early vessel blockages from forming. The stent has three stages before it disappears. These are revascularization, restoration and reabsorption. Revascularization is when the stent is initially placed and restores blood flow in the vessel. In the restoration phase the stent begins to degrade and the vessel regains some of its natural properties. In the reabsorption phase, the Absorb heart stent completely disappears leaving a natural vessel behind.

Studies of the Absorb Heart Stent
The Absorb heart stent has been extensively studied with over 100,000 patients treated as part of trials or registries that have documented its usefulness and safety when used in the right patient population. Followup of up to 5 years has been demonstrated. Importantly, not only does the stent disappear, but also it is comparable in usefulness to existing stents.Some studies showed that if not placed correctly there can be a possibility of stent blockage early on with the Absorb heart stent. It is therefore important to pay attention to detail when placing the stent. The artery needs to be prepared properly and the blockage dilated with the use of good-sized balloons. The artery needs to be of a decent size; the stent is not effective in vessels that are too small. After the stent is placed it should typically be dilated with a balloon that is appropriately sized to the vessel and the stent. Following the suggested protocols can minimize the risk of early stent problems. The Absorb heart stent can be visualized in the vessel using a technique known as optical coherence tomography.

by Dr. Mustafa Ahmed