Right ventricular ejection fraction determined in three projections

The right ventricular ejection fraction (RVEF) was successively determined in three projections in ten healthy volunteers aged 28-53, mean 37 years, with a first-pass technique using 99Tcm-labelled red blood cells and a gamma camera coupled to a computer. In the anterior-posterior projection (AP) the mean RVEF was 39.3%, range 26-49%, in the left anterior oblique (LAO) 43.7% (36-58), and in the right anterior oblique (RAO) 44.5% (36-54). These mean values do not differ significantly (P = 10%). The results from one of the subjects were withdrawn, as they deviated markedly from the general pattern, and the data were reanalysed from the remaining 9 subjects. Now the mean RVEF in the AP projection was 38.2%, which is significantly lower (P = 1%) than the corresponding RVEF of 44.3% in the LAO projection and of 45.2% in the RAO projection. Our results suggest that when using the classic first-pass technique, the right ventricle histograms will in any projection be influenced by the activity in the right atrium and the large vessels.