Clinical evaluation of poly(2-methoxyethylacrylate) in primary coronary artery bypass grafting

The introduction of cardiopulmonary bypass (CPB) has shaped surgical strategies for the correction of pediatric congenital anomalies as well as adult acquired cardiac disease. However, use of the extracorporeal circuit (ECC) is not without disadvantages. When blood is exposed to artificial surfaces of the ECC, plasma proteins become adsorbed to the synthetic surfaces (1,2). A systemic inflammatory response ensues with complement and leukocyte activation, and release of endotoxin and inflammatory mediators, which contributes to tissue injury (3,4). Systemic inflammatory response caused by bioincompatibility of the ECC is a major concern. In an effort to decrease the activation of biological systems as a consequence of the ECC, methods of attaching bioactive molecules to nonendothelialized surfaces of the ECC have been researched and introduced into clinical practice. Surface modification using heparin bonded to the surface of polymers in the ECC was one of the earliest interventional approaches to moderating surface contact activation. Heparin can be attached to materials according to various techniques: those that release heparin and those to which heparin is irreversibly bound (5). When used clinically, there is evidence that inflammation related to complement activation is decreased and this may be responsible for improved clinical outcomes after CPB (6,7). Besides heparin coating, other studies have investigated various types of surface modifications. First, the attachment of nitric oxide on the surface of the ECC has been shown to reduce platelet consumption and eliminate the need for systemic heparinization in an animal model (8). Second, silicone-coated oxygenators have been shown to suppress the release of proinflammatory marker, and were associated with better clinical outcomes (9). Third, surface-modifying additives revealed significantly less platelet deposition on the ECC, whereas complement activation measured by C3a were similar between experimental and control (CTR) groups (10). In addition, phosphorylcholine coating has been investigated clinically by De Somer et al., and appeared to have favorable effects on platelets (11). Recently, Terumo Corporation (Tokyo, Japan) has developed a surface modification for the ECC, which is engineered to influence protein adsorption and platelet adhesion. Poly(2-methoxyethylacrylate) (PMEA, X-coating™) is composed of an amphiphilic polymer, which is attributed to its hydrophobic and hydrophilic properties. Although PMEA is hydrophobic where it contacts the ECC surface, its blood contact surface is hydrophilic. The surface would have little tendency to react with blood components due to the outer side of the molecule being inactive chemically. There are promising data from in vitro and in vivo animal models supporting the potential improved biocompatibility of PMEA (12,13). The purpose of this investigation was to clinically evaluate PMEA-coated ECC in terms of hematological parameters, homologous blood transfusions, and clinical outcomes.