Lung pathology of complex congenital heart defect with diminished pulmonary blood flow but without aortopulmonary collateral artery and patent ductus arteriosus in infants and young children

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(P0.01).The internal diameter of small pulmonary artery(80.26±21.57 μm vs 58.53±10.29 μm;P0.05),AAR(46.59±14.43 vs 34.46±4.98;P0.01)and MLI(144.98±44.87 μm vs 108.39±20.76 μm;P0.05)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.