Factors influencing the quantitication of valvular regurgitation by gated equilibrium radionuclide angiography

Abstract

To test the clinical validity of the stroke volume ratio (SVR) and the factors influencing its value we determined it in a population of 41 patients free of valvular regurgitation. The SVR was estimated from multigated blood pool scans in left anterior oblique position by two methods. The first method followed the classical formula of the left to right ventricular stroke count ratio. The second method used the same formula except that the right atrial activity emanating from the area of right atrioventricular overlap as traced at right ventricular end-systole, was subtracted from the right ventricular stroke count. The SVR averaged 1.25 +/- 0.18 (range 0.97-1.80) by the first technique and 1.05 +/- 0.12 (range 0.82-1.36) by the second (P less than 0.001). In our results the SVR is not correlated to either ejection fraction or angiographically determined left ventricular volumes. Conversely the SVR is correlated with the left to right end-diastolic volume ratio evaluated from radionuclide counts measured at right and left ventricular end-diastole (r = 0.48, P less than 0.01). This may be due to variations in the area of right atrioventricular overlap, depending on the size of the ventricular chamber. It is postulated that the accuracy of SVR determination could be enhanced by subtraction of the right atrial activity from the right ventricular activity at end-systole. In patients free of valvular regurgitation the LV/RV stroke volume ratio approaches unity and the variability of the results is smaller. Interobserver and intraobserver variability is reduced using the Fourier phase approach.

Significance of gated equilibrium radionuclide ventriculography in quantification and follow up of valvular regurgitation

“…Due to some limitations based mainly in the overlap of right atrium and right ventricle, the significance of this technique is not yet clearly defined (Kress et al 1981;Lam et al 1981 ;Sorensen et al 1980; Thompson et al 1981;Urquhart et al 1981). In order to overcome these difficulties, some authors introduced modifications by using a slant hole collimator (Gandsman et al 1981), calculating left to right ventricular stroke count ratios directly from functional images (Gerson et al 1984;Makler et al 1983 ;Nicod et al 1982), correcting for right atrial overlap (Berthout et al 1984;Henze et al 1982) or combining first pass and equilibrium radionuclide ventriculography (Klepzig et al 1985 a).…”