Reproducibility of determination of right ventricular ejection fraction by radionuclide imaging: assessment by the statistical method of variance components.

Confidence limits for single and repeat measurements of right ventricular ejection fraction (RVEF) were established by means of a model based on the statistical method of variance components. A total of 80 subjects (age 23 to 74 years) were examined by two radionuclide methods 1) gated first-pass (fp) technique performed in a standard 30 degrees right anterior oblique projection, and 2) multigated equilibrium imaging (muga) in an individual left anterior oblique view, applying with both methods separate end-diastolic and end-systolic ventricular regions of interest. Values obtained by fp technique were clearly higher than those measured by the muga approach, and the correlation between them was only fair: RVEFmuga = 0.48 RVEFfp + 0.13; r = 0.73; SEE = 0.08. The 95% confidence limits for a single measurement were with the fp technique: 'true' RVEF = measured RVEF +/- 6 EF-units compared to +/- 16 units with the muga method. At repeat determination within an interval of four weeks, the minimal changes in measured RVEF that were statistically significant at the 5% level were with the fp technique +/- 8 units with the same observer on both occasions and +/- 9 units with different observers. Corresponding figures with the muga method were +/- 16 and +/- 22 units, respectively. The minimal changes in a subject's 'true' RVEF necessary to produce a significant change in measured RVEF were with fp technique +/- 14 units for the same observer and +/- 17 units for different observers, compared to +/- 30 and +/- 41 units with the muga method. In conclusion, the variability with the muga approach was far greater than with the fp technique and the consequent reproducibility so poor as to preclude meaningful measurement of RVEF by the muga method.