Heart valve testing
Since the foundation in 1971 the department of Cardiovascular Engineering CVE and its parent institutions are engaged in the development of in vitro testing of prosthetic heart valves.
In close collaboration with the company ac.biomed the heart valve labs of the department of Cardiovascular Engineering CVE is able to examine and assess any type of heart valve prostheses. This includes both, the compete hydrodynamic assessment according the valid standards ISO 5840 and FDA guidance draft October 14, 1994 and draft January 20, 2010 and evaluations during the development process of a new product. The listed links at the end of this page will guide you to more detailed information concerning the used test methods and test devices.
Prosthetic heart valves are used as a substitute for the damaged native heart valve for 50 years. Primarily heart valve prostheses were divided into two different categories: mechanical and biological prostheses.
Mechanical prostheses are totally manufactured from synthetic material and consist of valve housing and one or more valve leaflets. The leaflets are bedded inside the valve housing, a rigid ring made from pyrolytic carbon or metal alloy. The leaflets of nearly all available mechanical prostheses are made also from pyrolytic carbon, a very wear resistant and hemocompatible material. The benefit of mechanical heart valve prostheses is their good durability and reproducible manufacturing. Disadvantages are the requirement of an anticoagulation treatment and the appearance of cavitation and hemolysis.
Bioprostheses are basically made from biological tissue of different animal origin. They are classified in porcine and pericardial valves. Whereas porcine valves are made from aortic valve leaflets or the total aortic valve of pigs, the pericardial valves are manufactured from bovine or porcine pericardium. At both types of bioprostheses the tissue is fixated into a stent frame, which shapes and stabilizes the prostheses. So-called stentless bioprostheses, totally consist of biological material, are mainly manufacture from whole porcine aortic roots. Because of their physiological flow pattern, an anticoagulation treatment is usually not necessary after heart valve replacement with a bioprosthesis, but the durability of the devices is uncertain. They tend to calcify, biodegrade or fail structurally.
With the so-called percutaneous or TAVI (Trans Aortic Valve Implantation) valves a new type of heart valve prostheses was developed in the last years. This prostheses type is mainly a bioprosthesis. Porcine pericardium tissue or porcine valve leaflets are sutured into a stent frame of Nitinol. Different to the surgical valves the percutaneous valves are implanted minimal invasive. The prostheses are crimped, loaded into an application catheter and shifted to the implant position via a venous blood vessel or the apex region of the ventricle. There the prostheses are released, unfolded and fixated by means of radial forces only. The damaged native heart valves or a damaged bioprostheses are pressed against the aortic wall and the percutaneous valves ensure the valve function.
The introduction of the percutaneous valves led to a revised classification of the heart valve prostheses in the today valid standards; a distinction is drawn between surgical heart valve prostheses and prostheses minimal invasive implanted with catheter techniques. Regarding to the heart valve testing the variety of the different types of heart valve prostheses requires not only an adjustment of the testing standards and the development of new testing methods, but also make great demands on the test devices, which should be adapted to any prostheses type.
- Hydrodynamics and circulatory mock loops
- Durability assessment
- Particle Image Velocimetry PIV
- Bernoulli verification