目的：婴幼儿肺发育过程中，肺循环血量的改变影响肺外周血管的发育，导致肺组织的结构出现病理性改变。该研究利用形态半定量分析方法，了解不伴体-肺动脉侧支和动脉导管未闭的肺血减少型复杂先天性心脏病的婴幼儿肺细小动脉和肺泡间质的病理改变特点。方法选择有肺组织病理切片资料的56例婴幼儿不伴体-肺动脉侧支和动脉导管未闭的肺血减少型复杂先心病患儿作为病变组，年龄4～36月，包括法洛四联症34例和合并肺动脉狭窄的右室双出口7例、单心室9例、三尖瓣闭锁4例和完全性心内膜垫缺损2例。5例年龄4～18月非心、肺源性疾病死亡的婴幼儿作为对照组。采用显微镜形态半定量分析技术测量肺细小动脉内、外弹力板间距，计算平均中膜厚度百分比（MT%）和中膜面积百分比（MS%），单位面积肺细小动脉数目（APSC），单位面积肺泡数（MAN），平均肺泡内衬间隔(MLI)，肺实质占同切片肺总面积比例(PPA%)和单位面积肺泡数/肺细小动脉数比（AAR）。结果：先心病组的MT%，MS%，APSC和MAN降低，肺细小动脉内弹力板间距、AAR和MLI升高，与对照组比较差异有显著性，其余参数差异没有显著性。先心病组多数肺细小动脉形状不规则。结论：不伴体-肺动脉侧支和动脉导管未闭的肺血减少型复杂先心病的婴幼儿外周肺细小动脉中膜变薄、管腔扩张，单位面积肺细小动脉数目和单位面积肺泡数目减少，肺泡内径增大。

OBJECTIVE: The development of pulmonary vascular bed is strongly flow-dependent. Abnormal pulmonary blood flow leads to pulmonary pathological changes. This study aimed to observe the pathological changes of small pulmonary arteries and alveoli in complex congenital heart defect with diminished pulmonary blood flow but without aortopulmonary collateral artery (APCA) and patent ductus arteriosus (PDA) in infants and young children. METHODS: Autopsy pulmonary specimens obtained from 5 children who died of non-cardiovascular diseases were used as the control group (age: 4-18 months). Fifty-six children (age: 4-36 months) with complex congenital heart defect with diminished pulmonary blood flow but without APCA and PDA served as the study group, including 34 cases of tetralogy of Fallot, 7 cases of double outlet right ventricle with pulmonary stenosis, 9 cases of single ventricle with pulmonary stenosis, 4 cases of tricuspid atresia with pulmonary stenosis and 2 cases of complete atrioventricular septal defect with pulmonary stenosis. Pulmonary specimen sections were stained by hematoxylin-eosin and Weigert-Van Gieson. Percentage of media thickness (MT%), percentage of media section area (MS%), number of small arterial per square centimeter (APSC), mean alveolar number (MAN), mean linear intercept (MLI), proportion of parenchyma area in total area (PPA%) and alveolar to small arterial ratio per unit area (AAR) were measured by morphologic quantitative analysis.RESULTS: MT% (10.93±2.87% vs 15.08±2.51%), MS% (18.97±5.56% vs 25.04±3.87%) and APSC (202.43±67.45 vs 441.69±65.29) decreased significantly in the study group compared with the control group (P<0.01). The internal diameter of small pulmonary artery (80.26±21.57 μm vs 58.53±10.29 μm; P<0.05), AAR (46.59±14.43 vs 34.46±4.98; P<0.01) and MLI (144.98±44.87 μm vs 108.39±20.76 μm; P<0.05) increased significantly compared with the control group.CONCLUSIONS: The media of small pulmonary arteries becomes thinner, the lumen of small pulmonary arteries becomes larger, and the number of small arterial per square centimeter and the mean alveolar number are reduced in infants and young children with complex congenital heart defect with diminished pulmonary blood flow but without APCA and PDA.