Echocardiographic validation of the layer of maximum count method in the estimation of the left ventricular EF using gated myocardial perfusion SPECT: correlation with QGS, ECTb, and LVGTF.

AIM: Quantitative gated single-photon emission computed tomography (SPECT) (QGS), Emory Cardiac toolbox (ECTb), layer of maximum count (LMC), and left ventricular global thickening fraction (LVGTF) are four different methods designed to estimate the LV ejection fraction (EF). The third method (LMC) is relatively new and achieved good results in preliminary investigations. Thus, the objective of the study was to further assess the performance of the LMC versus two-dimensional echocardiography in the estimation of the LVEF in comparison with other methods.

METHODS: Data for 38 patients were analyzed retrospectively (27 males) with a mean age of 51+/-10 years. All patients underwent gated myocardial perfusion gated SPECT and two-dimensional echocardiography. EF estimated by the four methods and echocardiography were recorded and analyzed with paired t-test, Pearson's correlation coefficient, analysis of variance, and Bland-Altman plot.

RESULTS: The mean EF by echocardiography was significantly higher than QGS and LMC (P<0.0001 and P = 0.003, respectively), whereas it was significantly lower than ECTb and LVGTF methods (P = 0.02 and 0.001, respectively). QGS, ECTb, and LMC correlated significantly in the measurements of the EF with echocardiography (r = 0.844, 0.825, and 0.700, respectively); however, a lower correlation was found between LVGTF and echocardiography (r = 0.595). The agreement limits were (-7.6, 16.1) and (10.5, -15.7) for QGS and ECTb, respectively, whereas it was (-11.6, 19.6) and (-27.9, 15.7) for LMC and LVGTF, respectively. Pair-wise comparison has shown that the EF calculated by QGS was significantly lower than ECTb (P = 0.009) and LVGTF (P<0.0001), whereas it was not different from LMC (P = 0.928). For ECTb, the EF was significantly higher than LMC (P = 0.011), but was not different from LVGTF method (P = 0.173). Further, the EF by LMC was significantly lower than LVGTF method (P<0.0001).

CONCLUSION: The quantitative gated SPECT methods showed a significant correlation with echocardiography in the calculation of the EF. LMC method showed close results to those obtained by QGS and ECTb with similar variability versus the measurements made by echocardiography. This study has investigated the utility of using LMC method in clinical practice; however, it will be more feasible when it becomes independent and extensively validated with other accurate techniques and in different patient conditions.