摘要目的:利用超声左心室压力-应变环技术和单光子发射计算机断层扫描（SPECT）定量评估左束支传导阻滞（LBBB）对左心室结构、功能及心肌灌注的影响，并对LBBB犬进行组织病理学分析，探讨左束支传导阻滞性心肌病（LBBB-CM）心肌做功、心肌灌注与左心室重构病理改变之间的相关性。方法:选取14只雄性比格犬，消融左束支主干制作LBBB犬模型。采集LBBB犬造模前及造模后12个月的心电图、经食管超声心动图和动脉血压数据，获得左心室压力-应变环并分析造模前后的心肌做功参数，比较造模前基础状态与造模后12个月以上参数的差异。造模后12个月进行SPECT检查。另选7只月龄、体重相匹配的雄性比格犬作为对照组，对LBBB犬与对照组犬进行心脏大体解剖及组织病理学对比分析。分析LBBB犬心肌核素灌注（放射性摄取百分比）与心肌纤维化、心肌做功参数之间的相关性。结果:与造模前基础状态相比，造模后12个月左心室舒张末期容积增大［（20.78 ± 5.32）ml比（26.71 ± 7.94）ml， P = 0.003］，左心室射血分数降低［（59.17 ± 5.67）%比（47.69 ± 5.45）%， P<0.001］，左心室整体/节段纵向应变值、整体有用功及整体做功效率显著下降（均 P<0.05），而整体/节段无用功上升（均 P<0.001）。SPECT显示LBBB犬室间隔心肌灌注缺损，与侧壁对应节段相比，室间隔放射性摄取百分比明显降低（均 P<0.05）。LBBB犬心脏大体解剖和组织病理学分析显示心内膜增厚，局灶或片状分布的瓷白色改变，心肌细胞变性及纤维化等病理改变。与对照组犬相比，LBBB犬各节段心内膜及部分节段心肌层胶原纤维体积分数（CVF）明显升高（均 P<0.05）。节段心肌放射性摄取百分比与节段心肌做功（SMW）、节段心肌做功效率（SWE）呈正相关（ r s = 0.49、0.31，均 P<0.001），与CVF、节段心肌无用功（SWW）呈负相关（ r s = -0.51、-0.49，均 P<0.001）。 结论:LBBB是一种非良性心律失常，可导致左心室重构，心功能降低，心肌灌注异常及心内膜、心肌纤维化。超声心肌做功参数和心肌核素灌注作为无创性检查，可在一定程度上反映LBBB-CM左心室重构的程度。

abstractsObjective:To quantitatively evaluate the effects of left bundle branch block（LBBB）on left ventricular structure，function and myocardial perfusion using left ventricular pressure-strain loop and single photon emission computed tomography（SPECT），and to investigate the relationship between myocardial work，myocardial perfusion and pathological changes of left ventricular remodeling in left bundle branch block induced cardiomyopathy（LBBB-CM）.Methods:Fourteen male beagle dogs were selected，and the main trunk of the left bundle branch was ablated to create an LBBB dog model. Electrocardiogram（ECG），transesophageal echocardiography and arterial blood pressure data of LBBB dogs were collected before and 12 months after the ablation of left bundle branch trunk. Global and segmental myocardial work parameters were obtained by left ventricular pressure-strain loop. The differences of above parameters between baseline and 12 months after the ablation of left bundle branch were compared. SPECT was performed in LBBB dogs 12 months after the creation of LBBB. The hearts were harvested for anatomy observation and histopathological analysis in LBBB dogs and another 7 male beagle dogs（normal control group）matched by age and weight. The correlation between myocardial perfusion（percentage of regional tracer uptake）and myocardial work parameters，myocardial fibrosis in LBBB dogs were analyzed.Results:Compared with baseline，the left ventricular end-diastolic volume of 12 months after the ablation increased［（20.78 ± 5.32）ml vs（26.71 ± 7.94）ml， P = 0.003］，left ventricular ejection fraction decreased［（59.17 ± 5.67）% vs（47.69 ± 5.45）%， P<0.001］；left ventricular global/segmental longitudinal strain，global/segmental constructive work and global/segmental work efficiency decreased（all P<0.05），left ventricular global/segmental wasted work increased（all P<0.001）. Heterogenous perfusion defect was observed in LBBB dogs by SPECT，compared with lateral wall segments，the percentage of regional tracer uptake of septum was decreased（all P<0.05）. Gross anatomical and myocardial pathological changes were manifested as cardiomegaly，flaky or focal grayish thickening of endocardium，cardiomyocyte degeneration and fibrosis. Compared with normal control group，the collagen fiber volume fraction（CVF）in all segmental endocardium and partial segmental myocardium of LBBB dogs were significantly increased（all P<0.05）. Percentage of regional tracer uptake was positively correlated with segmental myocardial work（SMW）and segmental myocardial efficiency（SWE）（ r s = 0.49，0.31；both P<0.001），and negatively correlated with CVF and segmental wasted work（SWW）（ r s = -0.51，-0.49；both P<0.001）. Conclusions:Isolated LBBB is not benign，which can result in left ventricular remodeling，decreased cardiac constructive function，abnormal myocardial perfusion，endocardial fibrosis and myocardial fibrosis.The parameters of myocardial work assecsed by echocardiograpgy and myocardial perfusion，as non-invasive examination，can to some extent reflect the degree of left ventricular remodeling in LBBB-CM.