Performance of 8- vs 16 ECG-gated reconstructions in assessing myocardial function using Rubidium-82 myocardial perfusion imaging: Findings in a young, healthy population

Background: Current imaging guidelines recommend using at least 16 ECG gates when performing MUGA and cardiac SPECT to assess left ventricular ejection fraction (LVEF). However, for Rubidium-82 (⁸²Rb) PET, 8 ECG-gated reconstructions have been a mainstay. This study investigated the implications of quantitative assessments when employing 16 gate, instead of 8 gate, reconstructions for ⁸²Rb myocardial perfusion imaging (MPI).

Methods: The study comprised 25 healthy volunteers (median age 23 years) who underwent repeat MPI sessions employing ⁸²Rb PET/CT. We report LVEF, its reserve (stress LVEF - rest LVEF), and their repeatability measures (RMS method) obtained for 8- and 16 ECG-gated reconstructions.

Results: Similar LVEF and LVEF reserve estimates were found for the 8- and 16-gated reconstructions ([%] LVEF (8/16 gates): rest = 61 ± 6/64 ± 6, stress = 68 ± 7/71 ± 6, LVEF reserve (8/16 gates): 8 ± 3/6 ± 4, and all P ≥ 0.13). Similar test-retest repeatability measures were observed for rest and stress LVEF and their reserves [LVEF (8/16 gates); Rest = 4.5/4.6 (P = 0.81), Stress = 3.5/3.2 (P = 0.33), LVEF reserve = 46.7/49.3 (P = 0.13)].

Conclusion: In healthy subjects, 8 and 16 ECG gates can be used interchangeably if only volumetric assessments are desired. However, if filling and emptying rates are of interest, a minimum of 16 ECG gates should be employed.