April 17th, 2012

Why Make A Stent Out of Cornstarch?


Why the interest in “disappearing” stents?

Drug-eluting stents (DES) release drugs from durable polymer coatings on the stent that suppress neointimal proliferation, thereby reducing the risk of restenosis compared with bare metal stents (BMS).  However, the use of DES is associated with an increased risk of very late (>1 year) stent thrombosis compared with BMS.  Several mechanisms have been proposed for this phenomenon, including delayed endothelialization, chronic arterial inflammation, hypersensitivity reactions (eosinophilic infiltration), and incomplete stent apposition with vessel remodeling.  These problems can potentially be solved by using polymers and/or stents that resorb. 

What happens if you make the polymer disappear?

A biodegradable polymer-based DES allows controlled drug release followed by subsequent degradation of the polymer coating, ultimately rendering the stent surface similar to that of a BMS and devoid of a chronic inflammatory stimulus.  A recent published pooled analysis of individual patient data from the ISAR-TEST 3, ISAR-TEST 4, and LEADERS randomized trials showed that biodegradable polymer DES reduce the risk of stent thrombosis at 4 years in patients undergoing PCI when compared to conventional DES.

What happens if you make the entire stent disappear?

A recently released study evaluated the long-term (i.e., 10 year) safety of the first-in-man fully biodegradable coronary stent made of poly-l-lactic acid (i.e., a cornstarch-based material).  Between September, 1998, and April, 2000, 50 patients with 63 lesions were treated electively with 84 biodegradable non-DES.  The investigators noted acceptable major adverse cardiac event rates — similar to those of BMS — without stent recoil or vessel remodeling  (see table).

Event Rate at 10 yrs


Freedom from death


Freedom from cardiac death


Freedom from target lesion revascularization


Freedom from death, nonfatal MI, and
target lesion or vessel revascularization


Although the investigators expected the stent to degrade within 6 months, complete degradation actually took up to 3 years in some subjects.  Two definite scaffold thromboses (1 subacute, 1 very late) were noted: the former occurred in a patient who discontinued antiplatelet therapy because of a bleeding gastric ulcer, the latter a decade after implantation of the biodegradable stent (i.e., it was totally resorbed) that appeared to be related to a sirolimus-eluting stent implanted proximally.

Do you think biodegradable stents are here to stay…..or will they disappear?

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