The blood flow pathway within a device, together with the biomaterial surfaces and status of the patient’s blood, are well-recognized factors in the development of thrombotic deposition and subsequent embolization. Blood flow patterns are of particular concern for devices such as blood pumps (i.e. ventricular assist devices, VADs) where shearing forces can be high, volumes are relatively large, and the flow fields can be complex. However, few studies have examined the effect of geometric irregularities on thrombus formation on clinically relevant opaque materials under flow. The objective of this study was to quantify human platelet deposition onto Ti6Al4V alloys, as well as positive and negative control surfaces, in the region of defined crevices (~50–150 µm in width) that might be encountered in many VADs or other cardiovascular devices. To achieve this, reconstituted fresh human blood with hemoglobin-depleted red blood cells (to achieve optical clarity while maintaining relevant rheology), long working optics, and a custom designed parallel plate flow chamber were employed. The results showed that the least amount of platelet deposition occurred in the largest crevice size examined, which was counterintuitive. The greatest levels of deposition occurred in the 90 µm and 53 µm crevices at the lower wall shear rate. The results suggest that while crevices may be unavoidable in device manufacturing, the crevice size might be tailored, depending on the flow conditions, to reduce the risk of thromboembolic events. Further, these data might be used to improve the accuracy of predictive models of thrombotic deposition in cardiovascular devices to help optimize the blood flow path and reduce device thrombogenicity.

Objective: Ideal heart valve solutions aim to provide thrombosis-free durability. A scaffold-based polycarbonate urethane urea tissue-engineered heart valve designed to mimic native valve microstructure and function was used. This study examined the acute in vivo function of a stented tissue-engineered heart valve in a porcine model. Methods: Trileaflet valves were fabricated by electrospinning polycarbonate urethane urea using double component fiber deposition. The tissue-engineered heart valve was mounted on an AZ31 magnesium alloy biodegradable stent frame. Five 80-kg Yorkshire pigs underwent open tissue-engineered heart valve implantation on cardiopulmonary bypass in the pulmonary position. Tissue-engineered heart valve function was echocardiographically evaluated immediately postimplant and at planned study end points at 1, 4, 8, and 12 hours. Explanted valves underwent biaxial mechanical testing and scanning electron microscopy for ultrastructural analysis and thrombosis detection.Results: All 5 animals underwent successful valve implantation. All were weaned from cardiopulmonary bypass, closed, and recovered until harvest study end point except 1 animal that was found to have congenital tricuspid valve dysplasia and that was euthanized postimplant. All 5 cases revealed postcardiopulmonary bypass normal leaflet function, no regurgitation, and an average peak velocity of 2 m/s, unchanged at end point. All tissue-engineered heart valve leaflets retained microstructural architecture with no platelet activation or thrombosis by scanning electron microscopy. There was microscopic evidence of fibrin deposition on 2 of 5 stent frames, not on the tissueengineered heart valve. Biaxial stress examination revealed retained postimplant mechanics of tissue-engineered heart valve fibers without functional or ultrastructural degradation.Conclusions: A biodegradable elastomeric heart valve scaffold for in situ tissueengineered leaflet replacement is acutely functional and devoid of leaflet microthrombosis.

Objectives: The present study compared physical, mechanical, and biologic characteristics of four clinically available surgical sealants for cardiovascular repair. Methods: BioGlue®, PreveLeak®, Tridyne ™ VS, and Coseal® were compared for the following properties: hydrated swelling, cytocompatibility, burst strength, biaxial stretching (elasticity), and in vitro degradation. Results: Sealants showed a wide range of swelling upon hydration. By gravimetric and volumetric measurement, swelling was greatest for Coseal® followed by Tridyne ™ VS, BioGlue®, and PreveLeak®. Tridyne ™ VS was the most cytocompatible based on Alamar Blue assay results, supporting 85% cell survival compared to 36–39% survival with the other sealants. All sealants withstood pressure above mean arterial pressure (70–110 mmHg) and physiologic systolic blood pressure (90–140mmHg) in an ex vivo arterial flow burst model; lowest peak pressure at failure was PreveLeak® at 235±48 mmHg, highest peak pressure at failure was BioGlue® at 596±72 mmHg. Biaxial tensile testing showed no differences in elasticity between ex vivo porcine aorta and carotid arteries and Tridyne™ VS or Coseal® while BioGlue® and PreveLeak® were significantly stiffer. In vitro degradation time for Coseal® was 6 days, and 21 days for Tridyne ™ VS. No degradation was observed in BioGlue® or PreveLeak® for 30 days. Conclusions: Although all sealants withstood supraphysiological arterial pressure, there were differences in characteristics that may be important in clinical outcome. Coseal® degradation time was short compared to other sealants whereas BioGlue® and PreveLeak® showed a significant compliance mismatch with native porcine carotid artery. Tridyne™ VS was significantly more cytocompatible than the other three sealants.