Hydrodynamic performance of Carbomedics valves in double valve replacement

Most patients undergoing double valve replacements have reduced myocardial capacity. However, little is known about the influence of valve sizes on myocardial energy consumption in double valve replacement. This study was designed to supply hydrodynamic data for the proper selection of sizes in double valve replacement. A mock loop system was used to measure the energy consumption of CarboMedics valves at conditions resembling rest (5 L/min) and moderate exercise (9 L/min). All combinations of aortic valves size #21 to #27 with mitral prosthesis sizes #25 to #29 were tested separately. Larger size aortic prostheses revealed remarkably less energy consumption up to size #27. Under high flow (9 L/min) this effect was more pronounced. In contrast, mitral valve prosthesis sizes #25 to #29 had similar hydrodynamic data. At low flow conditions (5 L/min) no significant benefit was found with the use of a larger mitral valve. Only a reduction of less than 10 percent of total energy consumption could be achieved with the use of a mitral valve larger than #25 at 9 L/min flow. In conclusion there is no hydrodynamic reason for using a valve larger than #25 in the mitral position for patients who exercise moderately. Continuous reduction of cardiac work can be expected with the use of the largest possible aortic prosthesis up to size #27 at rest and at moderate exercise.