Pressure Recovery (PR).
When the ventricle contracts, blood flow converges beyond the aortic valve (AV) at the vena contracta (VC) and is laminar in its central portion, but forms flow vortices and Eddy currents in the sinuses around the central laminar flow with temporary energy dissipation. Upstream from the aortic valve at the vena contracta, the flow vortices rejoin the central flow and the flow velocity decelerates leading to partial recovery of pressure. In this example, energy dissipation accounts for 40 mm Hg of net pressure gradient, while 20 mm Hg is recovered up stream. Since echocardiography ignored pressure recovery, echocardiography mean gradient (ECHO MG) is recorded as 60 mm Hg, while catheterization MG (CATH MG) accounts for pressure recovery and is recorded at 40 mm Hg. In aortic stenosis, pressure recovery maybe relatively minimal compared with total convective acceleration and energy dissipation. However, is some cases of aortic stenosis and in normally functioning prosthetic valves, it compromises a larger portion and hence accounts for echocardiography/catheterization discordance
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