Estimation of left atrial size using ultrasound

A technique for estimating the size of the left atrium was developed using pulsed reflected ultrasound. The technique consisted of placing the transducer in the third intercostal space of the recumbent patient and recording echoes from the interventricular septum, the atrioventricular wall, and the posterior wall of the left atrium. The distance between the atrioventricular wall and the left atrial wall echoes represented the left atrial dimension (LAD). This measurement was obtained on 21 normal subjects and 47 patients undergoing cardiac catheterization. Twenty-eight of these patients had selective left atrial cineangiocardiograms as part of their diagnostic workup. The correlation between the ultrasound LAD measurements and the size of the left atrium as determined by the cineangiocardiograms was excellent (r = 0.9120, p < 0.001). This estimate of left atrial size was better than was obtained with routine cardiac fluoroscopy. Among the normal subjects the mean LAD was 3.1 ± 0.5 cm. with a range of 1.8 to 4.0 cm. When divided by body surface area the normal range was 1.2 to 2.0 cm. per M. 2 The measurements on the 47 patients undergoing cardiac catheterization were consistent with known left atrial size in patients with various cardiac abnormalities. Patients with pure mitral valve disease or bivalvular disease had consistantly high LAD measurements. The measurements were smaller but still usually abnormal in patients with pure aortic valve disease and were normal in patients with atrial septal defects. The advantages of this ultrasound technique over currently available methods for estimating left atrial size are convenience and accuracy. This examination eliminates the hazards and inconvenience of angiocardiography; and by obtaining a true internal dimension of the left atrium rather than merely visualizing one or two of the chamber's external borders, this procedure is more accurate than routine cardiac fluoroscopy and chest roentgenograms.