Comparison of the Echo-Doppler- and Radionuclide Angiography- Derived Regurgitation Fraction in Isolated Chronic Aortic Regurgitation

Abstract

The regurgitation fraction (RF) despite dependence on many factors remains a valuable quantitative index in chronic aortic regurgitation (AR) assessment. In order to verify échocardiographie (Echo) estimation of this parameter a comparison with radionuclide ventriculography (RNY) values was done. 35 patients with chronic pure AR, 30 male, 5 female, mean age 35.5 ± 11.2 years (18-70 years) were examined. Echo RF was calculated according to the formula: RF = [(LVSY - RVSV)/LVSV] x 100, where LVSY and RVSV are the left and right ventricular stroke volumes; LVSV or RVSV = CSA x VFI, CSA = n (D/2)^2, where CSA = aortic or pulmonary cross-sectional area, D = aortic or pulmonary ring diameter, VFI = aortic or pulmonary velocity flow integral. On the following 0-22 days (mean 7 ± 5.12), gated equilibrium RNA with red blood cell-labelled 99mTc were done. All images were obtained with a small field of view Cardiac (Siemens) gamma camera with a Max Delta computer system. The study was done with a high-sensitivity colimator and contained 6 million counts (250 thousand/frame). RF calculation is based on the visual images of the end-systolic, enddiastolic counts and stroke volume of both ventricles. RNA RF was calculated according to the formula: RNA RF = [(LVEDc - LVESc) - (RVEDc - RVESc)/(LVEDc - LVESc)] x 100, where LVEDc, RVEDc, LVESc, RVESc are the left and right ventricular end diastolic and end systolic stroke counts. The mean Echo RF value was: 54.29 ± 12.44% (21-74%) and the meanRNVRF 52.06 ± 13.16% (17—80%). The correlation coefficient between the Echo and RNV RF was r = 0.68, p < 0.0001 (Pearson’s test). Excluding 9 patients with normal left ventricular internal diastolic dimension (LVIDD) (< 5.6 cm) increased the correlation coefficient up to r = 0.84, p < 0.0001. Using paired Student’s t test no significant difference between Echo and RNV RF was found. The mean difference of the RF values obtained with the two methods was -2.23 ± 10.17%. The highest discrepancy has occurred only in 4 patients with normal LVIDD (-30 to +25%).