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1 Heart Valve Laboratory, John P. Robarts Research Institute, London N6A 5K8; 2 Department of Medical Biophysics, University of Western Ontario, London N6A 5C1; and 3 Division of Cardiology, London Health Sciences Centre, University Campus, London, Ontario N6A 5A5, Canada
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 (
O2) of seven porcine aortic valve cusps
in vitro at 37°C using a chamber with a Clark oxygen sensor. Mean
DO2 and
O2 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
O2 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.
tissue engineering; metabolic activity
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