Left atrial enlargement is a significant finding, usually indicating elevated left ventricular end-diastolic pressure. An increased tracheal carinal angle has been reported as one indicator on chest radiography of left atrial enlargement. This study retrospectively compared echocardiographically determined left atrial size with carinal angle on plain films. Enlarged left atria and paired, age-matched normal left atria by echocardiography were selected. The carinal angle was measured on roentgenogram (standard and portable films) by goniometer. The left atrium could be accurately predicted to be larger than 5.0 cm in diameter if the carinal angle was 100° or greater. A carinal angle greater than 100° is an easy, inexpensive, reliable method of predicting left atrial enlargement.
(Arch Intern Med. 1991;151:307-308)