Causes of stent failure can include poor placement, the use of bare metal stents, and mechanical fatigue. Success rates can vary by device and medical professional; people with substantial experience in stenting procedures, for example, can experience more positive patient outcomes. In some cases, stent failure happens from the start, when the device cannot be placed properly and another measure needs to be considered to address a narrowed artery.
Stents are used to address stenosis, a medical complication where the walls of an artery thicken and narrow, limiting blood supply. It is a particular concern around the heart, where interruptions in blood supply could cause a heart attack. In an angioplasty procedure, a medical professional can remove built up plaque on the wall of the artery before inserting a stent to hold it open. Stents fail if soft tissue grows over them, narrowing the artery again, or when they buckle, break, or collapse.
One potential cause of stent failure is iatrogenic, meaning that it is the doctor’s fault. Some damage to the walls of the artery can occur during placement, which increases the chance of soft tissue growth over the stent. Doctors with more experience working in advanced facilities can be more successful, as can those using devices they know well. Problems with stent design can be a factor as well; some products are hard to insert, for example, which increases the risk of tissue damage.
Another issue is the construction of the stent. Historically, these devices were made from bare metal, which created an excellent matrix for soft tissue to grow on. Many devices now are designed to slowly secrete drugs over time to block clotting and cell growth. Drug eluting stents, as they are known, tend to experience a higher success rate. If there are concerns about stent failure, this type of device may be recommended.
Mechanical fatigue can be a factor in stent failure. Metals used in medical devices are subjected to extensive testing, but microscopic analysis of failed stents can show signs of cracks, pitting, bending, and fractures. These indicate that some metals may not be suitable for long-term use, as they could break down over time. Strain might cause the stent to fail, putting the patient at risk of a serious medical complication if the issue cannot be identified in time. When a failure is linked to obvious metal fatigue, it can be reported to a medical database, allowing regulators to monitor the ongoing safety of specific devices on the market and ultimately determining if they should remain available for sale.