Comparison of cardiac dimensions by transesophageal and transthoracic echocardiography

Transesophageal echocardiography (TEE) has advanced rapidly as a valuable cardiovascular diagnostic technique. As the use of TEE increases, so does the importance of well-defined normal cardiac measurements. Presently, few data exist on the accuracy of M-mode TEE-derived measurements. Therefore in 81 adult patients, TEE-derived M-mode measurements were compared with analogous measurements that were made by standard M-mode transthoracic echocardiography (TTE). The TTE and TEE measurements did not differ in aortic root diameter, end-diastolic left ventricular diameter, end-diastolic septal wall versus anterior wall thickness, or end-diastolic posterior wall versus inferior wall thickness. These TEE measurements were within 95% confidence limits of TTE measurements. TEE-derived left atrial diameter (3.5 ± 0.8 cm) was less than that derived by TTE (3.8 ± 0.8 cm; p < 0.001) and fell outside of the 95% confidence interval. TTE left atrial size could be estimated as follows: TTE-derived left atrial diameter = TEE-derived left atrial diameter × 0.6 + 1.5 cm. In conclusion, M-mode measurements of aortic root diameter, left ventricular diameter, and wall thicknesses as derived by TTE and TEE are comparable. TEE-derived left atrial diameter may be used to estimate the left atrial TTE measurement. TEE-derived M-mode measurements are likely to be most useful when results of TTE are technically inadequate.