Low septal to lateral wall 18F-FDG ratio is highly associated with mechanical dyssynchrony in non-ischemic CRT candidates

Background: In order to better understand the concept of mechanical dyssynchrony, a promising hallmark of cardiac resynchronization therapy (CRT) response, we investigated its effect on regional myocardial metabolism and myocardial blood flow (MBF) in non-ischemic CRT candidates. Results: Thirty consecutive non-ischemic CRT eligible patients underwent static F-18-FDG and resting dynamic N-13-NH3 PET/CT. F-18-FDG uptake and MBF for septal and lateral wall were analysed and septal-to-lateral wall ratios (SLR) were calculated. Based on the presence of mechanical dyssynchrony (septal flash and/or apical rocking) on echocardiography, patients were divided into 2 groups, with (n = 23) and without (n = 7) mechanical dyssynchrony. Patients with mechanical dyssynchrony had significantly lower F-18-FDG SUVmean in the septum compared with the lateral wall (5.58 +/- 2.65 vs 11.19 +/- 4.10, p < 0.0001), while patients without mechanical dyssynchrony had a more homogeneous F-18-FDG distribution (7.33 +/- 2.88 vs 8.31 +/- 2.50, respectively, p = 0.30). Similarly, MBF was significantly different between the septal and lateral wall in the dyssynchrony group (0.57 +/- 0.11 ml/g/min vs 0.92 +/- 0.23 ml/g/min, respectively, p < 0.0001), whereas no difference was observed in the non-dyssynchrony group (0.61 +/- 0.23ml/g/min vs 0.77 +/- 0.21 ml/g/min, respectively, p = 0.16). F-18-FDG SLR, but not MBF SLR, was associated with the presence of mechanical dyssynchrony and showed a significant inverse correlation with volumetric reverse remodeling after CRT (r = - 0.62, p = 0.001). Conclusions: Non-ischemic heart failure patients with mechanical dyssynchrony demonstrate heterogeneous regional metabolism and MBF compared with patients without dyssynchrony. However, only F-18-FDG SLR appeared to be highly associated with the presence of mechanical dyssynchrony.