Prosthetic valve replacement.

1 find it somewhat surprising that after twcnty years of valve replacement the subject is stiii a topic for discussion at major cardiac surgical meetings. This undoubt ediy reflects the status of valves today since there stili rernains no ideal vaive substitute. In fact in recent years there appears te be a general trend toward trying to preserve the patient's own natural valve by rather extensive recenstruction rather than resorting to valve replacement. Unfortunately, at the time ef surgery, relatively few valves iend themselves te recenstructive procedures Se that a valve substitute is necessary and the question then becomes as te what valve te employ. lf 1 were te be asked what valves we are currendy using at the Mayo Clinic, 1 would have te say neariy ali valve models. This is due not only te the diversity ef epinion among the surgeons, but also because the cheice ef the valve should vary according te the physiological and anatomical factors noted at the time of surgcry. A few years age Dr. McGoen and 1 extended Dr. Harken's criteria upon which valves should be assessed. These criteria were durability, hemodynamic characteristics, thromboemboiism, assurance ef function, availability and cheice ef size, ease of inser tiefl, and record of survival. These criteria stili seem valid today, aitheugh avaUable size and case of insertion are virtually equally achieved by ali vaive medeis; hewever, among the other criteria ali valves currentiy fali short in one er mere areas. Ther~fere the choice today is not which valve is the best, but which vaive compromises the patient the least. As a result, we are still not in a pesition te be offering valve replacement in the earliest phases of valvular heart disease but must wait until a degree ef myecardial decompensation occurs .that will justify inserting a iess than ideal vaive substitute. As the cemplication rate and mortality remains higher for mitral vaive replacement, we feel that functional limitation equivalent te nearly Ciass lii New York Heart Associa tiOfl lirnitatien be achieved before wc repiace a mitral valve while Class II disabiiity for aortic valve replacement seems indicated. Certainly awaiting this degree ef decempen sation takcs itS to)lI in myecardia~ reserve and the ultirnate improvemcnr of the patient is undoubtedly cempromised. Altcrnatively, however, even a normally functiening prosthctic valve is equivalent te moderate valvular dysfunction and alth~ugh the patients status may be temporariiy stabilizcd by valvcreplacerncnt, further …