Only about 10% of emboli actually cause infarction- Regarding morphologic consequences of embolic occlusion of pulmonary arteries - Robbins 7th/742 Why only 10% of emboli cause infarction?Because the lungs have a dual blood supply. In patients with adequate cardiovascular function, the bronchial arterial supply can often sustain the lung parenchyma despite obstruction to the pulmonary arterial system. Pulmonary embolism usually causes infarction only when the circulation is already inadequate as in patients with heart or lung disease. For this reason, pulmonary infarcts tend to be uncommon in the young.Consequences of pulmonary embolismThe effects of pulmonary embolism depend mainly on the size of the occluded vessel, the number of emboli, and on cardiovascular status of the patients. The following consequences can result.1. AsymptomaticMost pulmonary emboli (60% to 80%) are clinically silent because they are small. With time, they undergo organization and are incorporated into the vascular wall.2.   Sudden death (cardiovascular collapse)Massive pulmonary embolism may result in instantaneous death, without occurrence of chest pain and dyspnea.3.   Acute cor pulmonale (Acute right heart failure)Numerus small emboli may obstruct most of the pulmonary circulation resulting in acute heart failure.4.   Pulmonary infarctionEmbolic obstruction of small end-arteriolar pulmonary branches can cause pulmonary infarction. About three-fourths of all infarcts affect the lower lobes, and in more than half, multiple lesions occur. Characteristically, they extend to the periphery of the lung substance as a wedge with the apex pointing toward the kilns of the lung. The pulmonary infarct is classically hemorrhagic infarct.5.   Pulmonary hemorrhageEmbolic obstruction of medium-sized arteries may result in pulmonary hemorrhage.6.   Pulmonary hypertensionMultiple emboli over time may cause pulmonary hypertension with right heart failure.