Thompson Kerry, Saab George, Birnie David, Chow Benjamin J W, Ukkonen Heikki, Ananthasubramaniam Karthik, Dekemp Robert A, Garrard Linda, Ruddy Terrence D, Dasilva Jean N, Beanlands Rob S B
Division of Cardiology, National Cardiac PET Centre, University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
J Nucl Med. 2006 Nov;47(11):1763-8.
Left bundle branch block (LBBB) is common in patients with heart failure (HF) and contributes to left ventricular (LV) dysfunction. The abnormal septal motion may alter septal metabolic demand but this has not been well characterized in patients with ischemic cardiomyopathy (ICM) and LV dysfunction. The aim of this study was to determine the effect of LBBB on septal metabolism in patients with ICM, LV dysfunction, and LBBB.
Fifty-three patients with LV dysfunction and ICM were identified: 34 with LBBB, 19 with normal QRS (</=100, control patients). PET using (18)F-FDG and (82)Rb was used to measure myocardial glucose metabolism and perfusion, respectively. Perfusion-metabolism differences were determined. Scar scores (matched decreases in (18)F-FDG and (82)Rb), mismatch scores (hibernating myocardium with decreased (82)Rb relative to (18)F-FDG), and reverse-mismatch (R-MM) scores (reduced (18)F-FDG relative to (82)Rb) were assessed in the septum and lateral wall.
(18)F-FDG uptake in the septum was reduced in patients with LBBB (64.0% +/- 15.4%) compared with control patients (74.9% +/- 14.3%; P < 0.05). Mean septal R-MM was greater in patients with LBBB (19.1% +/- 15.3%) versus control patients (4.7% +/- 10.6%; P < 0.05). However, 32% (11/34) of patients with LBBB did not demonstrate septal R-MM, 91% (10/11) of whom demonstrated lateral wall perfusion defects. Of the 68% (23/34) of patients with LBBB and septal R-MM, 52% (12/23) demonstrated lateral wall perfusion defects (P < 0.05). There was a significant difference in the percentage of the lateral wall with scar between those with septal R-MM (9.3% +/- 10.5%) and those without (19.9% +/- 14.3%; P < 0.05).
Previously, LBBB was believed to be characterized by reduced glucose metabolism relative to perfusion in the septum; however, this is not always the case in ICM. LBBB is not associated with septal R-MM in >30% of this patient population. Absence of this finding was often associated with lateral wall perfusion defects, suggesting an alteration in the metabolic demand on the septum. This may have implications for HF therapies such as resynchronization and requires further study.
左束支传导阻滞（LBBB）在心力衰竭（HF）患者中很常见，并导致左心室（LV）功能障碍。室间隔运动异常可能会改变室间隔代谢需求，但这在缺血性心肌病（ICM）和LV功能障碍患者中尚未得到很好的描述。本研究的目的是确定LBBB对ICM、LV功能障碍和LBBB患者室间隔代谢的影响。
确定了53例LV功能障碍和ICM患者：34例有LBBB，19例QRS正常（≤100，为对照患者）。分别使用（18）F-FDG和（82）Rb进行PET检查，以测量心肌葡萄糖代谢和灌注。确定灌注-代谢差异。评估室间隔和侧壁的瘢痕评分（（18）F-FDG和（82）Rb的匹配降低）、不匹配评分（冬眠心肌，（82）Rb相对于（18）F-FDG降低）和反向不匹配（R-MM）评分（（18）F-FDG相对于（82）Rb降低）。
与对照患者（74.9%±14.3%）相比，LBBB患者室间隔的（18）F-FDG摄取减少（64.0%±15.4%；P<0.05）。LBBB患者的平均室间隔R-MM（19.1%±15.3%）高于对照患者（4.7%±10.6%；P<0.05）。然而，32%（11/34）的LBBB患者未表现出室间隔R-MM，其中91%（10/11）表现出侧壁灌注缺损。在有室间隔R-MM的LBBB患者中，68%（23/34）的患者中有52%（12/23）表现出侧壁灌注缺损（P<0.05）。有室间隔R-MM的患者与无室间隔R-MM的患者相比，侧壁瘢痕百分比有显著差异（9.3%±10.5%对19.9%±14.3%；P<0.05）。
以前，人们认为LBBB的特征是室间隔葡萄糖代谢相对于灌注减少；然而，在ICM中情况并非总是如此。在超过30%的该患者群体中，LBBB与室间隔R-MM无关。未发现这一现象通常与侧壁灌注缺损有关，提示室间隔代谢需求发生改变。这可能对诸如再同步化等HF治疗有影响，需要进一步研究。
