In vivo strain measurements of a prosthetic aortic valve.

Up to the present, stress forces on prosthetic heart valves have been studied primarily in an in vitro state and have been derived with a fair amount of estimation. Because of the practical and clinical implications, such as forces that may cause fabric wear or material deterioration, we felt that in vivo determination would be worthy of investigation. A microminiature strain gauge was secured to each leg of a non-cloth-covered prosthetic aortic valve and connected to a dual-beam oscilloscope. Strain measurements were first determined in a pulse duplicator with a blood analogue solution and physiological pressures and flow. The valve was also implanted into a dog in the subcoronary position and strain again measured. In vivo strain was found to be approximately 57 per cent of strain on a prosthetic aortic valve, in vitro, under the conditions of this experiment. This represents the first time that strain and force on a prosthetic aortic valve have been determined directly in the intact animal.