Spontaneous variability of left ventricular ejection fraction assessed with the Cardioscint

A miniature, non-imaging caesium iodide nuclear probe optically coupled to a photodiode (the 'Cardioscint') has been developed which, in conjunction with a modified personal computer, is capable of continuous on-line monitoring of left ventricular function and ST-segment level at the bedside. The purpose of this study was to assess the variability in ejection fraction over periods of time and to compare this variability with that of equilibrium gamma camera radionuclide ventriculography. Ten normal volunteers (nine male) of mean (S.D.) age 49 (10) years underwent semisupine radionuclide ventriculography using both gamma camera and Cardioscint in randomized order. The gamma camera recorded four consecutive acquisitions (mean of 7.2 min each) and the Cardioscint, using a 20 s acquisition time, recorded left ventricular function over 35 min per subject. The mean ejection fraction of the group by gamma camera was 52 (7)% and by Cardioscint was 54 (5)%. When the variability in ejection fraction by gamma camera was compared with the Cardioscint averaged over corresponding time periods (i.e. an average of 7.2 min), the mean coefficient of variation of the camera was 5.0% versus 2.9% for the probe system. Individual 20-s probe acquisitions over the total study duration (reflecting the short-term variability of the system) had a coefficient of variation of 5.1%. Thus the Cardioscint provides a stable continuous recording of ejection fraction. These volunteer data provide a basis for interpretation of data acquired in the clinical situation.