Abstract
BackgroundIn 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.ResultsThirty consecutive non-ischemic CRT eligible patients underwent static 18F-FDG and resting dynamic 13N-NH3 PET/CT. 18F-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 18F-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 18F-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 ± 0.23 ml/g/min vs 0.77 ± 0.21 ml/g/min, respectively, p = 0.16). 18F-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).ConclusionsNon-ischemic heart failure patients with mechanical dyssynchrony demonstrate heterogeneous regional metabolism and MBF compared with patients without dyssynchrony. However, only 18F-FDG SLR appeared to be highly associated with the presence of mechanical dyssynchrony.Trial registrationClinicaltrials, NCT02537782. Registered 2 September 2015.
Highlights
During the last decade, ventricular conduction disturbances have been shown to be associated with adverse cardiac remodeling and to contribute to the development of heart failure (HF) and an increased risk of allcause mortality [1]
Three patients had suboptimal quality of 18F-FDG scan and 1 patient underwent 99mTc-tetrofosmin perfusion scintigraphy instead of 13N-NH3 positron emission tomography (PET) scan. After excluding these studies from the analysis, 27/30 and 29/30 patients have successfully completed respectively a 18FFDG and 13N-NH3 PET scan. These scans were included in the further analysis independently of each other and were distributed between both patient groups as follows: 18F-FDG and 13N-NH3 scans belonged to the group of mechanical dyssynchrony while 6 18F-FDG and 7 13N-NH3 scans represented the group without mechanical dyssynchrony
The main finding of our study in non-ischemic cardiac resynchronization therapy (CRT) candidates is the regional heterogeneity of myocardial glucose metabolism and perfusion in the presence of left ventricle (LV) mechanical dyssynchrony, which can be attributed to the regional differences in myocardial loading conditions
Summary
Ventricular conduction disturbances have been shown to be associated with adverse cardiac remodeling and to contribute to the development of heart failure (HF) and an increased risk of allcause mortality [1]. Septal flash (SF) and apical rocking (AR), surrogate markers of mechanical dyssynchrony, have been shown to be associated with favorable CRT response [3]. Deeper insights into pathophysiological processes related to mechanical dyssynchrony are needed, including changes in perfusion and metabolism, in order to better understand the adverse cardiac remodeling and to further improve patient selection for CRT. 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) studies in patients with ventricular conduction abnormalities have shown regional changes in glucose metabolism with a relatively reduced glucose uptake in the septum compared with an increased uptake in the lateral wall [4, 5]. 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.
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