ATLANTA — A metal stent that provides scaffolding for a vessel wall for about 2 months before being absorbed was found safe and effective in a small, first-in-man trial in bioabsorbable stenting, Dr. Raimund Erbel reported at a conference sponsored by the American College of Cardiology.
“The absorbable metal stent is not just another stent. It represents a revolutionary leap forward in vascular interventional treatment,” said Dr. Erbel, principal investigator of the Clinical Performance and Angiographic Results of the Multicenter, Nonrandomized Coronary Stenting With Absorbable Metal Stents (PROGRESS-AMS) study.
In PROGRESS-AMS, investigators at nine medical centers treated 63 patients with a de novo lesion in a single coronary artery. Of the patients, 70% were men and 18% had diabetes. The target lesion was in the left anterior descending artery in 22 patients, in the left circumflex artery in 18, and in the right coronary artery in 23; 24% had a prior percutaneous coronary intervention. Predilation was performed in all patients, and postdilation was performed in 67% of patients.
The primary efficacy end point was major adverse cardiovascular events—defined as cardiac death, nonfatal MI, or ischemia-driven target vessel revascularization (TVR)—of lower than 30% at 4 months. This end point was achieved: The rate was 24%, all accountable to ischemia-driven TVR. There were no occurrences of in-stent thrombosis, myocardial infarction, or death.
The stent used in the study, made by Berlin-based Biotronik GmbH, is made of a magnesium alloy and is indistinguishable from a standard bare-metal stent in appearance, Dr. Erbel said. Magnesium was chosen because it is an essential element for humans, who have a daily requirement of 350 mg. Furthermore, it is a calcium antagonist, has antiarrhythmic properties, and is not associated with allergies, he noted.
Among the clinical advantages of a bioabsorbable stent is that it clears the vessel of useless metal once it has been revascularized. Patients who have had in-stent restenosis may accumulate layers of metal in the affected vessel, making it increasingly difficult to treat, said Dr. Erbel, of Essen (Germany) University, at the conference, which was also sponsored by the Society of Cardiovascular Angiography and Interventions.
Dr. Erbel noted that late stent thrombosis, a problem with drug-eluting stents, is reduced with an absorbable stent, because as it degrades the endothelium becomes smooth, regains function, and undergoes positive remodeling. Such a stent is also an important development in pediatric cardiology. Permanent stents cannot be used in children because the vessels grow. Surgery is the only way to remove a stent that is outgrown.
Another advantage of the magnesium stent is its visualization options. When using MRI or CT, the stent is transparent. With MRI, “We saw no stent, but saw a nice open vessel,” said Dr. Erbel, who is a consultant to Biotronik. However, with micro MRI, the struts can be seen because of higher resolution. And with intravascular ultrasound, one can “see the struts, nicely opposed to the vessel wall,” he said. Imaging showed that the stent degradation process took 2–3 months.
An absorbable stent reduces late stent thrombosis, a problem with drug-eluting stents. DR. ERBEL