Bileaflet valves

A CarboMetrics bileaflet valve or Medtronic Hall tilting disk mechanical valve in the aortic position, with normal left atrial size and normal sinus rhythm... 

FIGURE 44.3 A CarboMedics bileaflet valve with pyrolytic carbon leaflets and housing. (Courtesy of Sulzer-CarboMedics, Austin, TX.)... 

FIGURE 44.5 Cavitation bubbles visualized on the inflow side of the valves in vitro [Chandran et al 1994a] (a) Medtronic-Hall tilting disc valve (b) Edwards-Duromedics bileaflet valve (c) CarboMedics bileaflet valve. 

FIGURE 20.1 Orifice and profile views of representative bileailet and tiltingKiisk valves are provided in the upper and lower halves of the figure. Note the larger percentage of open orifice area present in the bileaflet valve. The tilting disk projects farther inKt the downstream ejection zone than the leaflets on the bileaflet valve. 

Currently, about 90,000 valve replacement procedures are conducted in the United States, with about 280,000 such procedures conducted around the world [13]. The world population is expected to increase from 6.1 billion in 2000 to 8.9 billion in 2050, with the percentage of people of the population over 65 years increasing from 6.9% of the world population in 2000 to 15.9% in 2050 [14]. This aging population of patients requiring heart valve replacement is estimated to triple by 2050, from -290,000 in 2003, to over 850,000 by 2050 [15,16]. The most commonly used valve replacements in the developed world are mechanical bileaflet valves and bioprosthetic valves. In developing countries, tilting disk and ball-and-cage valves continue to be used due to lower costs. Across all valves, aortic valves are most widely replaced, followed by the mitral valve, pulmonary valve, and tricuspid valve. 

The most commonly used mechanical valves around the world are tilting disk and bileaflet mechanical heart valves. Both valves have similar durability and the need for anticoagulation therapy, but the bileaflet valves have superior hemodynamic performance. The primary advantage of mechanical valves is their durability, which translates to lesser reoperation rates compared to bioprosthetic valves. The most commonly used bioprosthetic valves in clinical practice are made of bovine or porcine pericardial tissue, mounted on either a stented or stentless assembly. Bioprosthetic valves have significantly lower risk of thrombosis, so the patient does not need lifelong anticoagulant therapy. However, structural... 

FIGURE 77.5 (a) Velocity profile 13 mm downstream on the centerline for the St. Jude Medical bileaflet valve, at peak systole (b) velocity profile 13 mm downstream across the central orifice for the St. Jude Medical bileaflet valve, at peak systole (c) turbulent shear stress profile 13 mm downstream of the centerline orifice for the St. Jude Medical bileaflet valve, at peak systole (d) turbulent shear stress profile 13 mm downstream across the central orifice for the St. Jude Medical bileaflet valve, at peak systole. 

TABLE 77.2 Peak Phase-Averaged Velocities and Turbulent Shear Stresses Measured within the Hinge Region of Different Bileaflet Valve Designs... 

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