The Re-organization of Circulation in Lungs with Advanced Hypertensive Arteriopathy and Obstructed Vascular Bed. A Computer-aided Reconstruction of Lung Vasculature in Patients with Congenital Heart Disease

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Computered 3-D reconstruction of pulmonary vessels was performed on lungs from eleven patients with pulmonary hypertension secondary to congenital heart diseases, in order to visualize the distribution of vascular diseases and understand how the pulmonary circulation is re-organized by newly formed collaterals. Arteriopathy was within grade 3 of Heath ＆ Edwards classification in two patients, while in the others it was grade 4 or higher. Reconstruction disclosed that patients of lower grade had an arterial bed which was only partially and unevenly obstructed, whereas those of grade 4 or higher had increasingly uniform obstruction of the arterial bed, and this would account for the elevated resistance in these patients. Plexiform lesions were shown to develop usually in a monopodial artery arising laterally from a parent vessel; in contrast, fibrously occluded arteries prevailed in dichotomous branches at the treetops, suggesting some haemodynamic factors involved in the pathogenesis of arteriopathies. Collaterals were demonstrated to develop so as to bypass in various ways the obstructive diseases. The dilatation lesions, overriding a severely stenosed arteriolar segment, were shown to lead some of the blood away from the peripheral bronchial arteries and to the alveolar capillaries. Also, broncho-pulmonary arterial anastomosis proved to exist at more proximal levels, allowing pulmonary arterial blood to circumvent the obstruction. Thus the blood flow to the alveolar tissue is mainly sustained via two pathways, one through the minute channels contained in the plexiform lesions o intimal thickenings and the other, via "bypass type" collaterals which lead pulmonary arterial blood along the bronchial arteries.