When it comes to stents, thin is in. In order to meet clinical demands for enhanced stent delivery and flexibility, medical device OEMs are striving to push the envelope and produce platforms with increasingly thin struts. But as these diminutive designs hit the market, emerging issues such as shrinkage and longitudinal compression are beginning to cast a shadow on the performance and reliability of some thin-strut stents.
A case series published online in the journal EuroIntervention proved to be the catalyst for a recent industry frenzy focused on a potential flaw found in some thin-strut stents. Conducted by two UK-based physicians, the series drew attention to the observed vulnerability of Biosensors International's BioMatrix, Boston Scientific's Promus Element, and Medtronic's Endeavor stent to longitudinal compression.
"The move over the years has been for stents to have thinner struts and to have different designs that would make them more flexible and deliverable in very tortuous and calcified coronary arteries," Simon Walsh, a physician involved in the study, told the theheart.org. "That's been the trend across the industry--and it's been an advance--but we're starting to see that once we use the stents in some of our more challenging subsets of patients, there are some limitations."
Building on the buzz, organizers of the Transcatheter Cardiovascular/Therapeutics (TCT) conference tacked on several talks about longitudinal compression to the agenda mere days before the event. But while presenters at TCT relayed anecdotes of longitudinal compression in various stents, most downplayed the issue as relatively rare and cautioned against getting caught up in the hype. Several speakers also noted that stent design may not be the sole culprit--surgical technique may also be a factor.
The safety of thin-strut stent designs was again called into question, however, in a recent case report and accompanying editorial in the Journal of Interventional Cardiology. In the report, the journal's editor Cindy Grines, a cardiologist, and her colleagues detail a case in which a patient suffered a heart attack as a result of the deformation of a Boston Scientific Ion coronary stent. The thin-strut Ion paclitaxel-eluting platinum-chromium coronary stent system, which obtained FDA clearance in April, demonstrated deformation, accordioning, and shortening of about 35%, according to Grines. She described this stent shrinkage in her editorial as "disturbing."
Although Boston Scientific may have some explaining to do on behalf of its Ion system, other manufacturers of thin-strut stents don't need to go on the defensive just yet. But experts do seem to be attributing these performance issues to thin-strut stent platform designs. And in light of this heightened scrutiny, OEMs would be wise to reevaluate next-generation stent designs to ensure that, by pursuing thinner struts, they are not compromising longitudinal strength and integrity. Companies should also consider heeding TCT presenters' suggestions to adopt standardized longitudinal strength-testing protocols in order to allay cardiologists' concerns. After all, being thin isn't everything.