Bronchial compression by an enlarged left atrium in infants; a cause of hypovascularity of the left lung.

In three infants seen recently at our institution we noted signs of compression of the left main bronchus associated with enlarged left atria. None of our cases demonstrated the more usual signs of hyperinflation which are a hyperlucent lung field, depressed hemidiaphragm and mediastinal shift away from the affected side. In addition, hypoperfusion of the left lung was noted in each case. We believe that bronchial compression due to an enlarged left atrium, with consequent hypoxic vasoconstriction as a clinically significant entity, which is not well described and may be unappreciated in infants in whom the typical signs of hyperinflation are absent.