New Materials New Technology Gives PCI Surgery New Possibilities

At present, the most common procedure for treating coronary heart disease is the interventional treatment of coronary artery (PCI), commonly known as stent surgery. Since the success of the first PCI operation in 1977, the field of interventional therapy via the coronary artery has developed rapidly.

The balloon catheterization is constantly upgraded.

In 1977, German doctor Gruentzig first used a double-cavity cyatic catheter in coronary angioplasty, a technique considered one of the most important techniques of the time. In 1982, the guide wire and balloon were operated independently. In 1986, replaceable angioplasty was used in clinical practice, and the conductor and balloons were quickly replaced, a flexibility that allowed medical staff to treat lesions that had previously been difficult to reach and dilated.

The standard angioplasty balloon is semi-compliant and its diameter increases with increased pressure, but may not be applied evenly along the size of the balloon. The diameter of the non-conforming balloon will hardly increase with the increase of pressure, so the inflator is more uniform and less prone to bursting. In addition, non-conforming balloons can also be recharged with higher pressures to expand highly calcified stenosis of narrow blood vessels.

Bracket placement brings a new breakthrough.   

The initial coronary arterial angioplasty was not combined with the use of a heart stent. Although atherosclerosis plaques in the walls of diseased blood vessels can be effective in treating coronary artery stenosis, patients are prone to vascular closure within hours or days after cystic angioplasty surgery, often requiring emergency repeated dilation or bypass surgery. A study based on a population in the United States showed a high incidence of re-stenosis in vascular sections in patients who successfully underwent coronary angioplasty in the first few months of treatment. As a result, with technological innovations, today's coronary arterial cyocytic sacs are often combined with stent placement.

A common PCI treatment involves sending a catheter with a balloon through a femoral artery or a tibia to the narrowness of the heart's coronary veins, expanding the tube cavity by filling the balloon, improving blood flow, and then placing a heart stent at the end of the expanded stenosis to prevent re-stenosis. At present, PCI treatment technology is mature, high safety, treatment mortality is low, and the contrast agent allergy, heart encapsulation fluid, heart filling and other complications are relatively rare, in the field of coronary heart disease treatment more and more widely used.   

Four common PCI placements.

Currently, common implants in PCI surgery include bare metal stents, drug elution stents, drug-coated balloons, and bioabsorbable stents.

Bare metal bracket.

The introduction of bare metal stents is an important development of transdermal coronary artery intervention technology. Stent placement stabilizes acute surgical effects by eliminating the back-sitting force of blood vessels and fixing anatomical plaques and tissues that may hinder blood flow. In addition, vascular stenosis remodeling is the main factor of re-stenosis after cyatic angioplasty, and coronary stents can be a good way to avoid stenosis remodeling.

A bare metal bracket is usually made up of a series of metal hoops connected by a connector. Originally made of stainless steel, most brackets are now made of cobalt or platinum-chromium alloy, and the height and width of the rods are gradually decreasing. There are two main types of bare metal stents: a self-expanding stent, which is constrained by a guard, which is removed after the device is delivered, and a balloon dilating stent stent, which is mounted bareon on a balloon angioplasty catheter and inflates the catheter to expand the device. However, because of the technical limitations of the self-expanding stent and the easily causing endomelism hyperplation, the clinical application is dominated by the balloon expansion stent.

Initially, clinical trials were made to use bare metal stents in patients with failed cystic angioplasty. The results showed that the restination rate was significantly lower in patients who used stent and had no success in cystic angioplasty. However, thrombosis in the stent is the main limitation of bare metal stent placement. In 1994, two medium-sized multi-center randomization trials showed better results than balloon dilating bare metal stents compared to angioplasty. At the same time, however, the thrombosis rate of the stent is also high, and the powerful anticoagulant regimen also increases vascular complications. Ultimately, the therapeutic effect of PCI surgery was significantly improved thanks to the development of optimized drug regimens and the development of intra-coronary imaging technology, as well as the introduction of vascular pathways in the tibia (priority over femoral arteries).

The drug eludes the stent.

Currently, drug elution stents are generally considered a mature technique with good clinical efficacy and high safety, and can repeat clinical results data. These brackets are dominated by bare metal brackets made of stainless steel or cobalt-chromium, which, unlike bare metal brackets, are covered by drug carriers with anti-growth effects, including permanent polymers, biodegradable polymers or non-use polymers.

Currently, there are two main types of permanent polymer drug elution stents that are widely used: the fluoropolymer-based Ivemos elution stent and the zothmos hallows based on the Bi ol inx polymer, and the clinical effects of the two stents are similar.

Several EU CE-certified stents have been granted for the removal of biodegradable polymer drugs, one of which has been approved for use in the United States. Most biodegradable polymer drug elution stents have a conventional metal frame, and their metal substrates consist of polylactic acid or polylactic acid-co-ethanolic acid, which is converted into carbon dioxide and water, and the conversion process typically takes 6 weeks to 24 months, depending on the molecular weight and crystallinity of the polymer configuration. The advantage of biodegradable polymer drug elution stents is that there is no polymer residue on the support trunk and can reduce the occurrence rate of adverse events after bracket placement. However, while late follow-up results have shown that biodegradable polymer drug elution stents are more effective than first-generation polymer drug elution stents, there is no evidence that they are superior to current durable polymer drug elution stents in terms of long-term durability.

Drug-coated balloons.

Drug-coated balloon catheter technology applies the package to the surface of a conventional balloon catheter, which consists of an active drug and an apacing or excipient to prevent drug clumps and promotethe drug transfer from the spherical surface to the vascular wall.

To date, clinically successful drug-coated cyocytic angioplasty cases have been limited to coated balloons based on yew alcohol preparations, which provide favorable local tissue transport and binding capacity compared to other formulations. The challenge of coronary arterial drug-coated cyalot technology is to demonstrate the same or superior performance as the drug-removal stent, which already has excellent efficacy and safety, and studies have shown that the clinical effect of the stent is superior to angioplasty. Therefore, drug-coated cyostic angioplasty has not been widely used in coronary therapy. At present, the technology is mainly used in the field of peripheral vascular system therapy.

Bio-absorbable bracket.

Bioabsorbability brackets are made up of biodegradable materials, the most common of which are polymers, such as polylactic acid or magnesium alloys.

The Ivymos Eludican Stent (ABSORB) with a polylactic acid skeleton has been subjected to large-scale randomized trials. The results of the ABSORB II trial showed that the vascular diastolic response to nitroglycerin nitrate was not improved by angiogram measurement in 3 years after surgery compared with the conventional metal ivemole elution stent. However, the anti-narrowing effect of the replacement endpoint assessment through the late tube cavity loss is relatively good.

The ABSORB III study is by far the largest bioabsorbable stent randomized trial. The study found that the target lesions failure rate of 1 year after the bioabsorbable stent was not significantly changed compared with the ivmosh stent, but the incidence of stent thrombosis was higher within 1 year, and in 2 years after surgery, the incidence of bioabsorbable stent target lesions failure and target vascular myocardial infarction was higher, and the effect on stent thrombosis was not statistically significant. However, several studies have also shown that bioabsorbable stents have a higher risk of thrombosis than metal drug elution stents, and that the potential benefits of bioabsorbable stent technology may only be apparent after being fully bioabsorbed (THE ABSORPTION TIME OF THE ABSORBent stent is approximately 3 years). Currently, bioabsorbable stents are in the stage of large-scale clinical trials and have a follow-up period of more than 5 years. This new technology has potential advantages, but it also needs to be further optimized and addressed.