Oxygen diffusion and consumption of aortic valve cusps

Abstract

To maintain tissue oxygenation, normal aortic valves contain a vascular bed where tissue thickness is greatest. Avascular "living" tissue-engineered heart valves have been proposed, yet little information exists regarding the magnitude of valve tissue metabolic activity or oxygen requirements. We therefore set out to measure the oxygen diffusivity (DO2) and oxygen consumption (VO2) of seven porcine aortic valve cusps in vitro at 37°c using a chamber with a Clark oxygen sensor. Mean DO2 and VO2 were 1.06 × 10-5 cm2/s and 3.05 × 10-5·ml O2·ml tissue-1·S-1, respectively. When modeled as a three-layered structure by using these values and a boundary condition of 100 mmHg at both surfaces, the average aortic cusp predicted a central mean PO2 of 27 mmHg (range of 0-50 mmHg). The DO2 value obtained was similar to that found for other vascular structures, but because our studies were carried out in vitro, the VO2 measurements may be lower than that required by the functioning valves. These values provide an initial understanding of the oxygen supply possible from the cusp surfaces and the oxygen needs of the tissue.