Quantification of valvular regurgitation using radioisotopes.

Mitral and aortic regurgitations impose an abnormal volume overload on the left ventricle. Recent advances in radionuclide angiographic measurements of all cardiac volumes have made this a practical technique for the detection, quantification and functional assessment of valvular regurgitations and shunts. The method is based on the comparative evaluation of total and effective left ventricular stroke volume. In the radionuclide technique, the right ventricular stroke volume is most frequently used to represent the effective left ventricular stroke volume although techniques have been presented which used as reference the left ventricular stroke volume calculated from measurements of heart rate and cardiac output (Fick method or dye dilution or scintigraphic techniques). The technique can be performed either during first-pass or at equilibrium. Equilibrium measurements are performed in the left anterior oblique position. The stroke volume ratio and the regurgitant fraction are calculated. This technique has been shown to provide adequate quantitative measurements of mitral and aortic regurgitations. Its specificity is adequate with careful positioning and if regions of interest are determined and care is taken to exclude inadequate studies (as these can be prospectively recognized). The technique can separate moderate from severe regurgitation, provide follow-up values for both left ventricular volume and regurgitant fraction, and assess the effect of interventions on the amount of regurgitation. The technique is, however, not adequate to detect mild or minimal regurgitation. In conclusion, equilibrium scintigraphic measurement of valvular regurgitation is an attractive new technique for measuring valvular regurgitation. Its clinical value lies in its simplicity, its reproducibility and its wide applicability. Its accuracy will be improved by performance of gated tomographic acquisitions.