11. Occlusion of the main pulmonary arteries can kill the patient suddenly. Occlusion of small pulmonary arteries has no major immediate effect. Occlusion of a medium-sized branch of pulmonary artery can lead to a pulmonary infarction in a person with compromised cardiac or respiratory status. A pulmonary infarct is hemorrhagic because of the dual blood supply  from the non-occluded bronchial arteries which continue to supply blood, but do not prevent the infarction.