Implant material cardiovascular applications

Biomaterials have many cardiovascular applications (that is, pertaining to the heart, blood, and blood vessels). Heart valve implants are often mechanical devices. The presentation of a smooth surface is important, to reduce blood clotting and the loss of red blood cells. Vascular grafts are commonly constructed of Dacron a polyester material that integrates with surrounding tissues. Artifi-... 

Biologic materials for cardiovascular application are derived from bovine or porcine sources (Liao et al., 1992). They lend to have a better tolerability requiring less pharmacologic adjuncts such as anticoagulants therapy as in most of the cases an antiplatelet regimen is sufficient however, they lend to degrade over time either because of reabsorption or due to calcium deposition that alters the mechanical properties of the tissue (Butany and Leask, 2001). The pace of this process may vary widely according to individual differences and site of implant. 

Biomaterials have played a vital role in the treatment of cardiovascular diseases, examples of applications including heart valve prostheses, vascular grafts, stents, indwelling catheters, ventricular assist devices, total implantable artificial heart, pacemakers, automatic internal cardioverter defibrillator, intraaortic balloon pump, and more. A key requirement for materials in cardiovascular applications, particularly blood-contacting devices, is blood compatibility, that is, nonthrombogenic. Additional requirements include mechanical and surface properties that are application specific. Surveying the field of polymers used in cardiovascular applications reveals that PUs, polyethylene terephthalate (PET), and expanded PTFE (ePTFE) are the most commonly used. This section will review each of the three polymers followed by a brief introduction of other emerging polymers for use in the cardiovascular area. 

Hemolysis is determined by placing powder, rods, or extracts of a material in contact with human or animal plasma for about 90 minutes at 37°C (31). The amount of hemoglobin released into solution after lysis of the red cells in contact with the device is measured. When red cells undergo lysis, hemoglobin is released from the cells, and the absorbance from released hemoglobin is proportional to the amount of cell lysis. Extensive red-cell lysis is not desirable for devices that are to be implanted in the cardiovascular system. The measurement of hemolysis and its relevance is a question that should be addressed it each device application. 

MAJOR APPLICATIONS Biomaterial applications such as dermal implant, carrier of drugs, cell culture matrix, wound dressing, material for hybrid organ, drug delivery system, soft contact lens, tissue implants, cardiovascular graft, artificial heart, etc. Synthetic sausage casings in food industry. ... 

Blood-contacting materials have to fulfill particular requirements, as they are immediately exposed to all host defense mechanisms of the body. Thus, the contact of blood with foreign surfaces induces several cascade reactions and activation phenomena. These complex and highly interconnected reactions potentially create clinically significant side effects in the application of medical devices (e.g., cardiovascular implants, extracorporeal circulation, catheters) and interfere with the success of the medical treatments [64]. In certain cases, even the formation of thromboemboli or systemic inflammatory reactions were reported to occur as a consequence of the activation of coagulation enzymes and thrombocytes and/or the activation of the complement system and leukocytes (immune response) at the biointerfaces of the applied materials [65]. 

The history of extracellular matrix (ECM)-derived medical implants is one of innovation and reinvention that spans over seven decades of cardiovascular surgery. The applications of ECM-deiived implants in these fields are broad replacement of cardiac valves, reconstruction of arteries and veins, creation of hemodialysis access, extending the lifespan of vascular reconstructions, and repairing trauma. Although there are currently a large number of ECM-derived prosthetics available for human use, understanding their similarities and differences, as well as their overall position in the general arena of implantable devices, will allow continued evolution and new applications for these versatile ECM-derived materials. 

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