Hufnagel valve: the first prosthetic mechanical valve

Biomaterials in Valvular Heart Diseases

Valvular heart disease (VHD) occurs as the result of valvular malfunction, which can greatly reduce patient's quality of life and if left untreated may lead to death. Different treatment regiments are available for management of this defect, which can be helpful in reducing the symptoms. The global commitment to reduce VHD-related mortality rates has enhanced the need for new therapeutic approaches. During the past decade, development of innovative pharmacological and surgical approaches have dramatically improved the quality of life for VHD patients, yet the search for low cost, more effective, and less invasive approaches is ongoing. The gold standard approach for VHD management is to replace or repair the injured valvular tissue with natural or synthetic biomaterials. Application of these biomaterials for cardiac valve regeneration and repair holds a great promise for treatment of this type of heart disease. The focus of the present review is the current use of different types of biomaterials in treatment of valvular heart diseases.

Diamond Anniversary of Mechanical Cardiac Valve Prostheses: A Tale of Cages, Balls, and Discs

This year marks the 60th anniversary of the first aortic and mitral valve replacements using mechanical artificial prosthesis. The first caged-ball devices represented a milestone in cardiac surgery and in the treatment of valvular disease. The following decades witnessed a great evolution in mechanical valve technology providing, through frustrating complications and stimulating successes, more reliable models to be safely used in the clinical setting. This review pays tribute to pioneers of this field who made currently available the most advanced models of mechanical prostheses with extended records of durability and performance, to be used as reliable alternatives to biological devices.

Mechanical considerations for polymeric heart valve development: Biomechanics, materials, design and manufacturing

The native human heart valve leaflet contains a layered microstructure comprising a hierarchical arrangement of collagen, elastin, proteoglycans and various cell types. Here, we review the various experimental methods that have been employed to probe this intricate microstructure and which attempt to elucidate the mechanisms that govern the leaflet's mechanical properties. These methods include uniaxial, biaxial, and flexural tests, coupled with microstructural characterization techniques such as small angle X-ray scattering (SAXS), small angle light scattering (SALS), and polarized light microscopy. These experiments have revealed complex elastic and viscoelastic mechanisms that are highly directional and dependent upon loading conditions and biochemistry. Of all engineering materials, polymers and polymer-based composites are best able to mimic the tissue-level mechanical behavior of the native leaflet. This similarity to native tissue permits the fabrication of polymeric valves with physiological flow patterns, reducing the risk of thrombosis compared to mechanical valves and in some cases surpassing the in vivo durability of bioprosthetic valves. Earlier work on polymeric valves simply assumed the mechanical properties of the polymer material to be linear elastic, while more recent studies have considered the full hyperelastic stress-strain response. These material models have been incorporated into computational models for the optimization of valve geometry, with the goal of minimizing internal stresses and improving durability. The latter portion of this review recounts these developments in polymeric heart valves, with a focus on mechanical testing of polymers, valve geometry, and manufacturing methods.

The early days of vascular and heart valve prostheses: a historical review

This surgical heritage article provides a historical overview of the most important early advances of vascular- and valvular surgery, that lead to the development of currently used vascular- and valvular prostheses and materials. The first writings describing techniques in vascular surgery mainly focussed on hemorrhage control and date from around 1600 B.C. The strategy of vessel ligation was first mentioned in Western literature around 200 B.C. In the 18^th century, techniques of ligation were expanded towards attempts of vessel restoration. The first artificial vascular prosthesis was made in 1894. From this time on, vascular prostheses were used in animal experiments and around 1900 for the first time in humans. More than 60 years later, in 1952, the first mechanical heart valve prosthesis was implanted. Four years later, the first successful biological heart valve implantation followed. In 2000, a transcatheter heart valve was successfully implanted in a human for the first time. Over time, procedures and techniques became more efficient and effective. This led to new developments, such as the manufacturing of a tissue engineered blood vessel in 1986. Nowadays, dozens of different valve prostheses have been devised, both mechanical and biological. Still, no ideal model of vascular and heart valve prosthesis exists.

The aortic valve: structure, complications and implications for transcatheter aortic valve replacement

The aortic valve operates in a complex haemodynamic environment, opening and closing over 100,000 times a day. When complications arise, such as aortic stenosis, prognosis can be very poor, leading to death within the first few years. Surgical valve replacement is currently the standard treatment for aortic stenosis. A thorough understanding of the anatomy and function of the native valve is imperative when developing a prosthetic replacement that can withstand the complex demands of the heart. This review focuses on the anatomy, structure and disease of the aortic valve and the implications for a transcatheter aortic valve replacement (TAVR). Current complications with TAVR, such as major vascular bleeding, conduction disturbances and patient-prosthesis mismatch (PPM), can be overcome by reducing the delivery profile and through the use of more accurate imaging technologies to work towards a fully functional and durable prosthesis.