Measurements of ejection fractions (EF) determined by first-pass and gated equilibrium radionuclide angiography are widely believed to be equivalent. To compare these measurements in a large group of patients over a wide range of EF values, left ventricular (LV) and right ventricular (RV) EFs at rest were measured in 135 consecutive patients who underwent the 2 methods of radionuclide angiography within 1 hour: first-pass upright with a multi-crystal camera in the anterior projection and gated equilibrium supine with a single-crystal camera in the left anterior oblique projection. The population included 18 normal patients and 117 patients with various cardiac and pulmonary disorders. First-pass and gated equilibrium LVEF correlated well (r = 0.83, p <0.001), but the slope of the regression line was different from unity, with the first-pass values lower than the gated equilibrium values (0.51 ± 0.16 vs 0.56 ± 0.15, p <0.05 [mean ± standard deviation]). Among the 45 patients with a gated equilibrium LVEF of <0.50, the correlation (r = 0.84) was better than that for the 90 patients with a LVEF > 0.50 (r = 0.44, p <0.05). However, in the latter group, the correlation remained good in the 15 patients with cardiomegaly due to aortic or mitral regurgitation (r = 0.80). Inter- and intraobserver error was similar for both methods. In contrast, there was a poor correlation between first-pass and gated equilibrium RVEF, with the first-pass values higher than the gated equilibrium values (0.51 ± 0.11 vs 0.43 ± 0.11, p <0.01). Interobserver error was similar for both the methods, but intraobserver error was better for the first-pass method (p <0.05). Thus, there may be considerable variability in the radionuclide EF at rest in the same patient because of differences in the method of measurement. Caution is suggested when EF values that have been derived using different radionuclide methods are compared.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine