New method for calculating right ventricular ejection fraction using gated myocardial perfusion studies

Background: Quantification of right ventricular ejection fraction (RVEF) is important in patients who have right heart failure or cor pulmonale. When TI-201 was the primary radiotracer used to evaluate myocardial perfusion, the outline of the right ventricle could vary and was not visualized in most patients. However, visualization of the right ventricle has become easier with the use of Tc-99m-labeled myocardial perfusion agents. Purpose: This study describes a new method for quantifying RVEF using gated stress myocardial perfusion (GMP) slices. The results are compared with those of first-pass radionuclide ventriculography (FPRNA) in the same patients. Methods: Fifty-two consecutive patients referred for routine GMP imaging were included. After administration of Tc-99m tetrofosmin, all patients underwent FPRNA using a single crystal gamma camera and a GMP study. Regions of interest (ROI) were drawn to outline the right ventricular cavity at end diastole and end systole from three pairs of GMP slices. The RVEF was calculated from the number of pixels within the ROIs. The mean RVEF obtained using FPRNA and GMP imaging was 51.8 ± 10.8% and 51.9 ± 12.3%, respectively. The two methods showed good correlation with r = 0.81. In addition, there was no significant difference in the RVEFs calculated using these methods (P = 0.85). Bland-Altman analysis also showed good agreement between the two methods (limits of agreement + 14.4% to -14.0%, slope = 0.19). Intraobserver and interobserver correlation were evaluated by reanalyzing 12 patients using the new RVEF quantification method and were good at r = 0.87 and 0.82, respectively. Therefore, this is a new convenient method for evaluating RVEF as part of a routine tomographic gated myocardial perfusion study.