Heart valve replacement surgery: past, present and future

1. The present review covers the historical and present role of valvular surgery in treating heart disease and speculates what the future may be in this very important field of cardiac surgery. 2. One of the important elements of tissue valve replacement is durability and how to analyse the valves mathematically, so that the projected durability could be described from the observed period to an extended period. We found that the Weibull distribution is a very good mathematical method of describing the deterioration of tissue valves. 3. We also can see a very marked difference among different pericardial valves. The Carpentier-Edwards pericardial valve has tremendous durability compared with the previous generation of pericardial valves, namely the Ionescu-Shiley. 4. The incidence of structural valve deterioration varies according to the age of the patient at the time of implant. A very important feature to analyse in making a clinical decision with regard to the type of valve to implant is the age of the patient at the time of implantation, because this determines their long-term survival. 5. Another very important feature of valve replacement is the problem of valve thrombosis. This was the problem that we encountered in experimental animals and why it is so difficult to obtain a long-term survivor with mechanical valve replacement in dogs. Now, in humans, the incidence of thrombosis of these artificial valves is extremely low. 6. Another important feature of valve replacement is the incidence of late thromboembolism (TE). Differences in reports using the same valve are greater than differences between different prostheses and the average is approximately 1.5-2%/year incidence of TE. 7. We can conclude from this review that there has been significant progress in diminishing operative mortality and enhanced long-term survival following valve replacement over the past four decades. Increased durability of tissue valves has now become apparent, from the earliest application to the current time with glutaraldehyde-preserved pericardial valves. The late complication rates are approximately the same with all valve types, except that there is a dimunition in the possibility for valve thrombosis for tissue valves versus mechanical valves. Finally, anticoagulation continues to be required for mechanical valve replacement and we still require more durable tissue valves and freedom from anticoagulation for mechanical valves.