['Phase analysis of gated myocardial perfusion imaging (MPI) provides automated and reproducible assessment of left ventricular (LV) mechanical dyssynchrony (LVMD) (phase standard deviation [SD]). Many patients undergoing gated MPI have history of prior coronary artery bypass graft surgery (CABG). The latter is often associated with paradoxical septal wall motion (PSM). The effect of prior CABG and PSM on LVMD has not been evaluated.', "From the single-photon emission computed tomography (SPECT) and positron emission tomography (PET) MPI clinical database maintained at the Cleveland Clinic, we identified 200 consecutive patients with SPECT (100 control with normal LV ejection fraction [EF], MPI, and QRS\xa0<\xa0120\xa0ms; and 100 with LVEF\xa0<\xa035%), and 631 patients with LVEF\xa0<\xa035% with gated PET. Patients with QRS\xa0≥\xa0120\xa0ms, bundle branch block, ventricular pacing or isolated non-CABG surgery were excluded. There were 162 patients with gated SPECT (46 with prior CABG), and 568 with gated PET (220 with prior CABG) that were left for analysis. Phase SD was derived using Emory Cardiac Toolbox (ECTb) (for gated SPECT) and Corridor 4DM (4DM) (for gated SPECT and PET images). Multivariate linear regression analysis was performed to assess whether prior CABG was an independent predictor of worse LV mechanical dyssynchrony. After adjusting for patients' demographics, co-morbidities, medications, and MPI data, history of prior CABG was not and independent predictor of LV mechanical dyssynchrony (P\xa0=\xa0.67 with 4DM, P\xa0=\xa0.97 with ECTb) in patients undergoing gated SPECT or among patients undergoing gated PET imaging (P\xa0=\xa0.18)."] Does paradoxical septal motion from prior coronary artery bypass graft surgery impact left ventricular mechanical dyssynchrony by gated myocardial perfusion imaging?