Tag: stents

Categories : Cardiovascular Disease Surgeries & ProceduresTags :

Stop Aspirin after Stent to Reduce Bleeding in MI Patients, Study Suggests

On By ModernMedia
Percutaneous coronary intervention.
Percutaneous coronary intervention. Credit: Scientific Animations CC4.0

Withdrawing aspirin one month after percutaneous coronary intervention (PCI) in high-risk heart patients and keeping them on ticagrelor alone safely improves outcomes and reduces major bleeding by more than half when compared to patients taking aspirin and ticagrelor combined (also known as dual antiplatelet therapy or DAPT), which is the current standard of care.

These are the results from the ULTIMATE-DAPT study announced during a late-breaking trial presentation at the American College of Cardiology Scientific Sessions on Sunday, April 7, and published in The Lancet.

This is the first and only trial to test high-risk patients with recent or threatened heart attack (acute coronary artery syndromes, or ACS) taking ticagrelor with a placebo starting one month after PCI, and compare them with ACS patients taking ticagrelor with aspirin over the same period. The significant findings could change the current guidelines for standard of care worldwide.

“Our study has demonstrated that withdrawing aspirin in patients with recent ACS one month after PCI is beneficial by reducing major and minor bleeding through one year by more than 50 percent. Moreover, there was no increase in adverse ischaemic events, meaning continuing aspirin was causing harm without providing any benefit,” says Gregg W. Stone, MD, the study co-chair of ULTIMATE-DAPT, who presented the trial results.

“It is my belief that it’s time to change the guidelines and standard clinical practice such that we no longer treat most ACS patients with dual antiplatelet therapy beyond one month after a successful PCI procedure. Treating these high-risk patients with a single potent platelet inhibitor such as ticagrelor will improve prognosis,” adds Dr Stone.

The study analysed 3400 patients with ACS at 58 centres in four countries between August 2019 and October 2022. All of the patients had undergone PCI, a non-surgical procedure in which interventional cardiologists use a catheter to place stents in the blocked coronary arteries to restore blood flow. The patients were stable one month after PCI and were on ticagrelor and aspirin. Researchers randomised the patients after one month, withdrawing aspirin in 1700 patients and putting them on ticagrelor and a placebo, while leaving the other 1700 patients on ticagrelor and aspirin. All patients were evaluated between 1 and 12 months after the procedure.

During the study period, 35 patients in the ticagrelor-placebo group had a major or minor bleeding event, compared to 78 patients in the ticagrelor-aspirin group, meaning that the incidence of overall bleeding incidents was reduced by 55 percent by withdrawing aspirin. The study also analysed major adverse cardiac and cerebrovascular events including death, heart attack, stroke, bypass graft surgery, or repeat PCI. These events occurred in 61 patients in the ticagrelor-placebo group compared to 63 patients in the ticagrelor-aspirin group, and were not statistically significant – further demonstrating that removing aspirin did no harm and improved outcomes.

“It was previously believed that discontinuing dual antiplatelet therapy within one year after PCI in patients with ACS would increase the risk of heart attack and other ischaemic complications, but the present study shows that is not the case, with contemporary drug-eluting stents now used in all PCI procedures. Discontinuing aspirin in patients with a recent or threatened heart attack who are stable one month after PCI is safe and, by decreasing serious bleeding, improves outcomes,” Dr Stone adds. “This study extends the results of prior work that showed similar results but without the quality of using a placebo, which eliminates bias from the study.”

Source: The Mount Sinai Hospital / Mount Sinai School of Medicine

Categories : Implants and ProsthesesTags :

Non-toxic Liquid Metal Breaks Down Aluminium Medical Implants

On By ModernMedia
Photo by Louise Reed on Unsplash

By taking advantage of a phenomenon that is usually an engineering headache, MIT researchers have designed a liquid metal to safely disintegrate metal medical implants and drug depots when they are not needed anymore.

In their work published in Advanced Materials, the researchers showed that aluminium biomedical devices can be disintegrated by exposing them to a liquid metal known as eutectic gallium-indium (EGaIn). In practice, this might work by painting the liquid onto staples used to hold skin together, for example, or by administering EGaIn microparticles to patients.

According to the researchers, disintegrating metal devices in this way could eliminate the need for surgical or endoscopic removal procedures.

“It’s a really dramatic phenomenon that can be applied to several settings,” says senior author Giovanni Traverso, assistant professor of mechanical engineering at MIT and a gastroenterologist at Brigham and Women’s Hospital. “What this enables, potentially, is the ability to have systems that don’t require an intervention such as an endoscopy or surgical procedure for removal of devices.”

Breaking down metals

For several years, Traverso’s lab has been working on ingestible devices that could remain in the digestive tract for days or weeks, releasing drugs on a specific schedule.

Most of those devices are made from polymers, but recently the researchers have been exploring the possibility of using metals, which are stronger and more durable. However, one of the challenges of delivering metal devices is finding a way to remove them once they’re no longer needed.

Right now, removing the staples can actually induce more tissue damage

Vivian Feig, MIT POSTDOC & First Author

To create devices that could be broken down on demand inside the body, the MIT turned to liquid metal embrittlement. This process has been well-studied as a source of failure in metal structures, including those made from zinc and stainless steel. It is why metal liquids such as mercury are not allowed on aircraft.

“It’s known that certain combinations of liquid metals can actually get into the grain boundaries of solid metals and cause them to dramatically weaken and fail,” says first author Vivian Feig, an MIT postdoc. “We wanted to see if we could harness that known failure mechanism in a productive way to build these biomedical devices.”

One room-temperature liquid metal that can induce embrittlement is gallium. For this study, the researchers used eutectic gallium-indium, an alloy of gallium that scientists have explored for a variety of applications in biomedicine as well as energy and flexible electronics.

For the devices themselves, the researchers chose to use aluminium, which is known to be susceptible to embrittlement when exposed to gallium.

Gallium weakens solid metals such as aluminium in two ways. First, it can diffuse through the grain boundaries of the metal – border lines between the crystals that make up the metal – causing pieces of the metal to break off. The MIT team showed that they could harness this phenomenon by designing metals with different types of grain structures, allowing the metals to break into small pieces or to fracture at a given point.

Gallium also prevents aluminium from forming a protective oxide layer on its surface, which increases the metal’s exposure to water and enhances its degradation.

The MIT team showed that after they painted gallium-indium onto aluminium devices, the metals would disintegrate within minutes. The researchers also created nanoparticles and microparticles of gallium-indium and showed that these particles, suspended in fluid, could also break down aluminium structures.

On-demand disintegration

While the researchers began this effort as a way to create devices that could be broken down in the gastrointestinal tract, they soon realised that it could also be applied to other biomedical devices such as staples and stents.

To demonstrate GI applications, the researchers designed a star-shaped device, with arms attached to a central elastomer by a hollow aluminium tube. Drugs can be carried in the arms, and the shape of the device helps it be retained in the GI tract for an extended period of time. In a study in animals, the researchers showed that this kind of device could be broken down in the GI tract upon treatment with gallium-indium.

The researchers then created aluminium staples and showed that they could be used to hold tissue together, then dissolved with a coating of gallium-indium.

“Right now, removing the staples can actually induce more tissue damage,” Feig says. “We showed that with our gallium formulation we can just paint it on the staples and get them to disintegrate on-demand instead.”

The researchers also showed that an aluminium stent they designed could be implanted in oesophageal tissue, then broken down by gallium-indium.

Currently, oesophageal stents are either left in the body permanently or endoscopically removed when no longer needed. Such stents are often made from metals such as nitinol, an alloy of nickel and titanium. The researchers are now working to see if they could create dissolvable devices from nitinol and other metals.

“An exciting thing to explore from a materials science perspective is: Can we take other metals that are more commonly used in the clinic and modify them so that they can become actively triggerable as well?” Feig says.

Initial toxicity studies in rodents showed that gallium-indium was non-toxic even at high doses. However, more study would be needed to ensure it would be safe to administer to patients, the researchers say.

Source: