Wave propagation and reflection in the canine aorta: analysis using a reservoir-wave approach.

BACKGROUND Our objective was to demonstrate wave propagation and reflection in the canine aorta. Recently we proposed that aortic pressure is the instantaneous sum of wave-related or "excess" pressure and reservoir or windkessel pressure. Accordingly, in this research we calculated reservoir pressure and subtracted it from measured pressure to identify the change in pressure due to forward- or backward-travelling waves. METHODS In 8 anesthetized dogs, excess pressures were calculated from pressure and flow measurements at 4 locations along the aorta; wave intensity analysis was employed to identify wavefronts and the type of waves. RESULTS We found that forward compression and decompression waves generated by the left ventricle are reflected, first, from a negative or "open-end" reflection site near the renal arteries (32.0 ± 0.8 cm [SEM] from the aortic root) and, second, from a positive site in the femoral arteries (65.3 ± 2.8 cm or 54.9 ± 2.1 cm, based on 2 alternative extrapolation techniques). CONCLUSIONS Aortic wave propagation and reflection can be demonstrated clearly and directly by wave intensity analysis after volume-related changes-changes in reservoir or windkessel pressure-in aortic pressure are accounted for.