Figure 4.

Haemodynamic considerations of AS. In a patient with severe AS, blood flow accelerates prior to the valve (flow acceleration region marked). The jet contracts in order to fit through the anatomical orifice and continues to contract for a short period, forming the effective orifice. Doppler indices of AS measure the severity of obstruction at the level of the effective orifice. In the ascending aorta, there is a degree of ‘pressure recovery’.