Heart valves regulate blood flow through the heart. The mitral and tricuspid valves (AV) are inlet valves located between the upper chambers (atria) and the lower chambers (ventricles). The aortic and pulmonary valves are outlet valves (SV) located in the arteries leaving the heart.
Heart valve failure causes:
- Stenosis – narrowing that limits blood flow. Stenosed valves may, in some cases, be treated via heart catheterization that inflates a balloon to separate valve cusps.
- Regurgitation – backward leaking, where valve flaps don’t close tightly and blood flows in the wrong direction. Treatment usually means surgical replacement of the valve.
Faulty heart valves can either be repaired or replaced. Traditional treatment involves open heart surgery – a highly invasive procedure that includes cutting through the sternal bone, stopping the heart and repairing or replacing the valve with an artificial heart valve.
Researchers have been looking for a minimally invasive intervention that can be performed without stopping the heart and without opening the chest, thereby minimizing pain, hospital stay, recovery time, and risk of infections. Trans-catheter aortic valve implantation (TAVI) provides a promising treatment for high risk patients that cannot undergo open heart surgery. The trans-catheter aortic valve is made of three cusps or leaflets sutured on a stent-like metal frame that can be crimped on a balloon, inserted in the groin or in the chest, and carefully guided towards the heart.
STI has acquired a wealth of experience in the manufacturing of metal frames for trans-catheter aortic valves by supporting the development of various types of artificial heart valves and providing contract manufacturing services to a tier-1 company operating in this specific niche.
The metal frame of a heart valve can be made from Stainless Steel (SS316LVM), Cobalt Chrome or Nitinol. The metal frame has a crimped diameter of 6-8mm and an expanded diameter varying between 21mm to 29mm, depending on the patient.
Existing frame fabrication methods include wire braiding or knitting and laser tube cutting. Today, most heart valve frames are being fabricated by laser cutting metal tubes of various diameters, lengths and wall thickness.
Balloon-expandable frames made of stainless steel and cobalt chrome alloys undergo annealing to relieve internal stresses, soften the metal, improve elongation rate, lower the risk of strut breakage, and improve fatigue resistance. Self-expanding frames utilize the elastic properties of Nitinol and require a different process called shape-setting to set the expanded diameter of the frame and fix the transition temperature and affects the radial force.
Post laser processing steps may include: mechanical deburring, pickling, electropolishing, passivation and cleaning. These steps result in a high-quality biocompatible product having a bright, shiny surface, free of defects, and improved corrosion resistance.
Visual and dimensional inspections carried out throughout the manufacturing process ensure that the final product meets the customer’s specifications. Quality assurance inspections use high-resolution optical microscopes, automatic digital micrometers, and video inspection systems. STI’s frame manufacturing procedures adhere to EN ISO 13485 and ISO 9001 quality standards.