Impact of strut dimensions and vessel caliber on thrombosis risk of bioresorbable scaffolds using hemodynamic metrics

Abstract

Bioresorbable scaffolds (BRS) promise to be the treatment of choice for stenosed coronary vessels. But higher thrombosis risk found in current clinical studies limits the expectations. Three hemodynamic metrics are introduced to evaluate the thrombosis risk of coronary stents/scaffolds using transient computational fluid dynamics (CFD). The principal phenomena are platelet activation and effective diffusion (platelet shear number, PSN), convective platelet transport (platelet convection number, PCN) and platelet aggregation (platelet aggregation number, PAN) were taken into consideration. In the present study, two different stent designs (thick-strut vs. thin-strut design) positioned in small- and medium-sized vessels (reference vessel diameter, RVD=2.25 mm vs. 2.70 mm) were analyzed. In both vessel models, the thick-strut design induced higher PSN, PCN and PAN values than the thin-strut design (thick-strut vs. thin-strut: PSN=2.92/2.19 and 0.54/0.30; PCN=3.14/1.15 and 2.08/0.43; PAN: 14.76/8.19 and 20.03/10.18 for RVD=2.25 mm and 2.70 mm). PSN and PCN are increased by the reduction of the vessel size (PSN: RVD=2.25 mm vs. 2.70 mm=5.41 and 7.30; PCN: RVD=2.25 mm vs. 2.70 mm=1.51 and 2.67 for thick-strut and thin-strut designs). The results suggest that bulky stents implanted in small caliber vessels may substantially increase the thrombosis risk. Moreover, sensitivity analyses imply that PSN is mostly influenced by vessel size (lesion-related factor), whereas PCN and PAN sensitively respond to strut-thickness (device-related factor).

Small vessel coronary artery disease: How small can we go with myocardial revascularization?

“…This approach was thought to provide similar benefits as DES, at same time being minimally invasive. Conversely, the first-generation lactic acid BRS was shown to confer greater risk of subacute, late, and very late stent thrombosis and a higher rate of TLR, most likely due to the design of thick lactic acid struts [70,71]. This led to contraindication for these devices to be used in routine clinical practice outside of clinical trials and recommendation for prolonged dual antiplatelet therapy > 12 months [21].…”

Personalized, Mechanically Strong, and Biodegradable Coronary Artery Stents via Melt Electrowriting

“…These devices were made from poly- l -lactic acid (PLLA), and while it gave the device the required biodegradation properties, the material lacked the required mechanical properties . As a result, the stents required significantly thicker struts (∼150 μm) in order to possess sufficient mechanical properties, compared to permanent metal stents, such as Synergy or Xience, which have strut thicknesses of ∼80 μm. ,− The thicker struts contributed to failure of the devices by exposing more pro-thrombogenic material within the vessel lumen, promoting inflammation, and causing significant pro-thrombogenic changes in the shear stress experienced by endothelial cells and platelets. ,, …”

Medical device innovations for cardiovascular, ophthalmologic and otolaryngologic applications

“…Quite recently, the approach of so called 'smart implants' has been incorporated into the RESPONSE consortium in order to include sensors, as well as energy supply technologies as another future enabling toolbox for cardiovascular implants (pressure monitoring, leadless pacing) and beyond. Furthermore, versatile numerical tools are being developed for the structural mechanical and fluid dynamical assessment of implants and implant/host interaction [8]. The field of medical device technology as addressed by RESPONSE is of high social relevance.…”