COMPARISON OF THE ECHO-DOPPLER-DERIVED AND RADIONUCLIDE ANGIOGRAPHY-DERIVED REGURGITATION FRACTION IN ISOLATED CHRONIC AORTIC REGURGITATION

The regurgitation fraction (RF) despite dependence on many factors rem ains a valuable quantitative index in chronic aortic regurgitation (AR ) assessment. In order to verify echocardiographic (Echo) estimation o f this parameter a comparison with radionuclide ventriculography (RNV) 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 = [(LVSV - RVSV)/LVSV] x 100, where LVSV and RVSV are the left and right ventricular stroke volumes ; LVSV or RVSV = CSA x VFI, CSA = pi (D/2)(2), where CSA = aortic or p ulmonary cross-sectional area, D = aortic or pulmonary ring diameter, VFI = aortic or pulmonary velocity flow integral. On the following 0-2 2 days (mean 7 +/- 5.12), gated equilibrium RNA with red blood cell-la belled Tc-99m were done. All images were obtained with a small field o f 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 v isual images of the end-systolic, end-diastolic counts and stroke volu me of both ventricles. RNA RF was calculated according to the formula: RNA RF = [(LVEDc - LVESc)- (RVEDc - RVESc)/(LVEDc - LVESc)] x 100, wh ere 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 mean RNV RF 52.06 +/- 13.16% (17-80% ). The correlation coefficient between the Echo and RNV RF was r = 0.6 8, p < 0.0001 (Pearson's test). Excluding 9 patients with normal left ventricular internal diastolic dimension (LVIDD) (less than or equal t o 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 obtain ed with the two methods was -2.23 +/- 10.17%. The highest discrepancy has occurred only in 4 patients with normal LVIDD (-30 to +25%).