Comparison of left atrial dimensions by transesophageal and transthoracic echocardiography

Left atrial (LA) size, as determined by transthoracic echocardiography (TTE), predicts the risk of atrial fibrillation and stroke and the success of cardioversion. Transesophageal echocardiography (TEE) is increasingly used in these clinical situations. However, unlike TTE, measurement of LA size by TEE has not been standardized. To validate TEE measurement, we determined LA dimensions in 4 standard views by TTE at the same time in 121 patients undergoing TEE. The mid-esophageal basal short-axis view at the level of the aortic valve (TEE 30-60) was the only view in which complete visualization of a LA axis of measurement could be obtained with an acceptably high yield (97.2%). The measurement from this view provided a value that had the highest correlation between TTE and TEE (r = 0.758, P <.0001, 95% confidence interval 0.68-0.86; bias 0.37 +/- 1 cm). Overall, TEE underestimated the LA dimension by 9% compared with TTE. These results suggest that the short-axis view at the level of the aortic valve is the preferred site for measuring the LA dimension by TEE.