Abstract

T he introduction of valve replacement surgery in the early 1960s has dramatically improved the outcome of patients with valvular heart disease.Approximately 90 000 valve substitutes are now implanted in the United States and 280 000 worldwide each year; approximately half are mechanical valves and half are bioprosthetic valves.Despite the marked improvements in prosthetic valve design and surgical procedures over the past decades, valve replacement does not provide a definitive cure to the patient.Instead, native valve disease is traded for "prosthetic valve disease," and the outcome of patients undergoing valve replacement is affected by prosthetic valve hemodynamics, durability, and thrombogenicity.Nonetheless, many of the prosthesis-related complications can be prevented or their impact minimized through optimal prosthesis selection in the individual patient and careful medical management and follow-up after implantation.The purpose of this article is to provide an overview of the current state of knowledge and future perspectives with regard to optimal prosthesis selection and clinical management after valve implantation. Types of Prosthetic Heart Valve DesignThe ideal valve substitute should mimic the characteristics of a normal native valve.In particular, it should have excellent hemodynamics, long durability, high thromboresistance, and excellent implantability.Unfortunately, this ideal valve substitute does not exist, and each of the currently available prosthetic valves has inherent limitations. Mechanical ValvesThree basic types of mechanical valve design exist: bileaflet, monoleaflet, and caged ball valves (Figure 1A, 1B, and1C). Caged Ball ValvesCaged ball valves, which consist of a silastic ball with a circular sewing ring and a cage formed by 3 metal arches, are no longer implanted.However, several thousands of patients still have caged ball valves, and these patients require follow-up. Monoleaflet ValvesMonoleaflet valves are composed of a single disk secured by lateral or central metal struts.The opening angle of the disk relative to valve annulus ranges from 60°to 80°, resulting in 2 distinct orifices of different sizes. Bileaflet ValvesBileaflet valves are made of 2 semilunar disks attached to a rigid valve ring by small hinges.The opening angle of the leaflets relative to the annulus plane ranges from 75°to 90°, and the open valve consists of 3 orifices: a small, slit-like central orifice between the 2 open leaflets and 2 larger semicircular orifices laterally.