Microtextured Materials for Circulatory Support Devices: Preliminary Studies

Abstract

Thromboembolic events (TE) associated with circulatory support devices are a major source of mortality and morbidity. Clinically, the lowest TE rates are claimed with devices that incorporate textured blood-contacting materials. The textured materials currently used in circulatory assist devices are composed of small, attached fibers that form the boundaries of connected cavities. These cavities entrap blood components to form a "neointimal" layer, which is believed to minimize thromboembolic events. We believe that the three-dimensional surface topography of blood-contacting materials is a major controlling factor in the formation of a stable neointimal layer upon the material. Particle-cast cavities were used to form geometric features in segmented polyurethane. This microtextured material was incorporated as part of a flexible blood-contacting surface in a blood pump that was implanted as a left ventricular assist device in calves. The structure, thickness, stability, and development of the neointimal layer were then evaluated. These preliminary studies have shown that a stable neointimal layer can be formed upon the particle-cast surfaces. The results also indicate that the cavity size on the particle-cast surfaces has a significant effect on neointimal adhesion. The methods employed can be used in the design of future circulatory support devices.

The effect of CD47 modified polymer surfaces on inflammatory cell attachment and activation

“…PVC tubing is a major component of cardiopulmonary bypass (CPB) circuits, and other blood contacting medical device surfaces, and represents a model polymer to test the hypothesis with respect to the neutrophil mediated acute inflammatory response, which occurs as a result of blood-material interactions. Similarly PU is used in long-term implants, such as pacemaker lead insulation [10] and left ventricular assist device blood contacting surfaces [11, 12], and thus was used in these experiments as a model surface to examine the chronic inflammatory effects mediated by MDM.…”

The Quest for Nonthrombotic Surface Modifications to Achieve Hemocompatibility of Implantable Devices

“…89 one hypothesis that was proposed to explain the formation of neointima on the sintered surface is the presence of a three-dimensional surface topography. Zapanta et al 90 casted cavities into a polyurethane polymer applied to the surface of a blood pump before implantation and noted the formation of a stable neointima. Additionally, adherence to the polymer correlated with the size of the cavity: the larger the cavities, the stronger the neointimal adherence.…”

“…Additionally, adherence to the polymer correlated with the size of the cavity: the larger the cavities, the stronger the neointimal adherence. 90 Patients implanted with the heartMate 1000 IP at 11 clinical centers in the united States were evaluated for thromboembolic complication at 62 ± 76 days in the setting of minimal systemic anticoagulation. Rose et al 84 found these patients to be at low risk for thromboembolic complications owing to the textured surface of their LVADs.…”

Surface coatings for ventricular assist devices

“…For instance, a textured surface was developed from sintered titanium microspheres fused to a substrate by the Thermoelectron Corporation during the 1980s. 55 Specifi cally, an approximately 1 mm wide and 1.9 mm long rectangular region could be laser machined at a time and, therefore, a larger surface was machined by repeating the same process. The surfaces were then heated under vacuum to sinter the microspheres to form voids between the individual microspheres, into which cells grew and adhered.…”