Prediction of pressure recovery location in aortic valve stenosis: an in-vitro validation study

Pressure recovery is a source of discrepancy between Doppler-derived and catheter aortic valve pressure drops. Pressure recovery occurs where the stenotic jet reattaches to the aortic wall. An equation to predict the jet reattachment location has been developed based on the density and viscosity of blood, the velocity in the stenotic jet, and the aortic root and valve areas. The study aim was to define the conditions where this equation is valid and could be accurately applied to Doppler echocardiographic data.

In a pulse duplicator, mean flow rates were varied between 2 and 5 l/min, and anatomic orifice areas between 0.32 and 2.85 cm2, to produce values of the ratio of anatomic valve area to the aortic root area (E) of 0.04 to 0.36. For each hemodynamic state, continuous-wave, pulsed-wave Doppler and color Doppler flow maps were recorded. Instantaneous flow rates and pressures proximal and distal to the valve were recorded. Calculated reattachment lengths were compared to measurements from color Doppler echocardiography.

Except for the smallest E value, there was a correlation between the predicted and measured jet reattachment lengths. The equation was good for predicted attachment lengths of less than 5 cm. Overestimation was seen for the smallest E value, representing a critically stenotic valve.

Except for the most severe stenoses, pressure drops for aortic valves are best measured with the aortic sensor placed approximately 5 cm above the aortic valve. For moderate stenoses, where pressure recovery is relevant, the site of fully recovered pressure can be predicted.