Prosthetic heart valves in the aortic position: engineering aspects

Aortic valve (AV) disease is a major contributor to cardiovascular morbidity, particularly in ageing populations. Although surgical and transcatheter AV replacement are established treatments, no current prosthesis fully reproduces the haemodynamic performance and durability of the native AV without clinical compromise. This review examines prosthetic heart valves in the aortic position from an engineering perspective, with emphasis on mechanical heart valves (MHVs) and bileaflet mechanical heart valves (BMHVs). The pathophysiology of aortic stenosis and aortic regurgitation is briefly outlined to contextualise replacement strategies, followed by a critical evaluation of bioprosthetic, mechanical, polymeric, homograft, autograft, and transcatheter valve technologies. The evolution of MHVs is reviewed alongside key considerations in material selection, including titanium alloys and pyrolytic carbon, and their associated mechanical and haemocompatibility properties. Fundamental fluid dynamic principles governing transvalvular flow, shear stress, and thrombogenicity are discussed in relation to valve geometry and hinge design. Anticoagulation requirements and their clinical implications are examined within the context of blood-material interactions. Despite significant advancements, contemporary BMHVs remain limited by non-physiological flow patterns and the lifelong need for anticoagulation therapy. Future development should prioritise improved leaflet kinematics, optimised hinge mechanics, and enhanced haemocompatibility to better approximate native valve function while reducing thromboembolic risk.