An obstructive embolus in the main stem or in one of the two principal branches of the pulmonary artery almost invariably causes sudden death as has been shown in the 100 cases of massive pulmonary embolism described in Part I. A large coiled-up embolus originating in a femoral vein produces only minimal pathologic changes in the lungs, such as edema and atelectasis. By contrast, when a medium-sized artery is blocked, characteristic changes take place in the lung parenchyma supplied by this vessel. As a result of the stoppage of blood flow, the alveoli and capillaries become markedly distended with red blood cells, and a red infarct forms. Pulmonary infarcts are seldom white or anemic but are almost always hemorrhagic, because of the rapid anastomosis which develops between the pulmonary and bronchial vessels, when obstruction occurs in the former. Later if the patient recovers the red cells degenerate, and the alveolar
GORHAM LW. A Study of Pulmonary Embolism: Part II. The Mechanism of Death; Based on a Clinicopathological Investigation of 100 Cases of Massive and 285 Cases of Minor Embolism of the Pulmonary Artery. Arch Intern Med. 1961;108(2):189–207. doi:10.1001/archinte.1961.03620080021003
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