The percentage of pulmonary emboli, that proceed to infraction, is approximately - (AIPG, 2011)
Only about 10% of emboli actually cause infarction- Regarding morphologic consequences of embolic occlusion of pulmonary arteries - Robbins 7th/ Page 742
a. Why only 10% of emboli cause infarction?
i. Because lungs have dual blood supply.
ii. In patients with adequate cardiovascular function, the bronchial arterial supply can often sustain the lung parenchyma despite obstruction to the pulmonary arterial system.
iii. Pulmonary embolism usually cause infarction only when the circulation is already inadequate as in patients with heart or lung disease.
iv. For this reason, pulmonary infarcts tend to be uncommon in the young.
b. Consequences of pulmonary embolism
• The effects of pulmonary embolism depend mainly on the size of the occluded vessel, the number of emboh and on cardiovascular status of the patients.
• The following consequences can result.
• Most pulmonary emboli (60% to 80%) are clinically silent because they are small.
• With time, they undergo organization and are incorporated into the vascular wall.
ii. Sudden death (cardiovascular collapse)
• Massive pulmonary embolism may result in instantaneous death, without occurence of chest pain and dyspnea.
iii. Acute cor pulmonale (Acute right heart failure)
• Numerus small emboli may obstruct most of the pulmonary circulation resulting in acute heart failure.
iv. Pulmonary infarction
• Embolic 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 apex pointing toward the hilus of the lung.
• The pulmonary infarct is cla sically hemorrhagic infarct.
v. Pulmonary hemorrhage
• Embolic obstruction of medium-sized arteries may result in pulmonary hemorrhage.
vi. Pulmonary hypertension
• Multiple emboli over time may cause pulmonary hypertension with right heart failure.