Quantification of Aortic Regurgitation

The aortic regurgitation fraction RGF is defined as ‘volume regurgitating from the aorta during diastole’ divided by Volume expelled into the aorta in the previous systole’. Assuming a competent mitral valve yields: $$ RGF\left( \% \right) = \left[ {(SV - FSV)/SV} \right] \times 100, $$ (1) where SV is the left ventricular stroke volume and FSV the ‘forward’ stroke volume. Conventional assessment of RGF requires determination of SV and FSV. SV is obtained from a contrast ventriculogram by volumetry (area-length or Simpson’s method). FSV is calculated from heart rate and cardiac output (CO), obtained usually by help of an indicator dilution technique. Since SV and FSV measurements are several minutes apart, RGF is affected by temporal variations of these two parameters. Moreover, all steps involved in the calculation of enddiastolic and endsystolic volumes of the left ventricle (LV) can produce together a considerable error of SV. The accuracy of FSV is no better than the accuracy of routine CO measurements. RGF can thus be very inaccurate.