A detailed histologic analysis of pulmonary arteriovenous malformations inchildren with cyanotic congenital heart disease

Introduction: Pulmonary arteriovenous malformations are a common cause of p rogressive cyanosis in children after cavopulmonary anastomoses, We analyze d the pulmonary histologic characteristics from children in whom pulmonary arteriovenous malformations developed after procedures that resulted in pul monary arterial blood flow devoid of hepatic venous effluent, Methods: We p erformed routine histologic studies, immunohistochemical staining, and elec tron microscopic analysis of peripheral lung biopsy specimens from 2 childr en with angiographically proven pulmonary arteriovenous malformations. Micr ovessel density was determined with a computer-assisted, morphometric analy sts system. Results: Histologic examination demonstrated large, dilated blo od vessels ("lakes") and clustered, smaller vessels ("chains") in the pulmo nary parenchyma. Microvessel density was significantly greater in these pat ients than in age-matched controls (P =.01). Immunohistochemistry demonstra ted uniform staining for type IV collagen and alpha-smooth muscle actin, we ak staining for the endothelial marker CD31 (cluster of differentiation, PE CAM-1), and negative staining for proliferating cell nuclear antigen. Elect ron microscopy revealed endothelial irregularity, a disorganized basement m embrane, and increased numbers of collagen and actin filaments beneath the endothelium. Conclusions: This study represents an attempt to characterize the histologic features of pulmonary arteriovenous malformations in childre n with congenital heart disease who have pulmonary arterial blood flow devo id of hepatic venous effluent, The histologic correlate of this condition a ppears to be greatly increased numbers of thin-walled vessels. Immunohistoc hemistry suggests that the rate of cellular proliferation is not increased in these lesions. The development of these techniques may provide a standar dized histologic approach for this condition and aid in understanding its e tiology.