Size-Adjusted Left Ventricular Outflow Tract Diameter Reference Values: A Safeguard for the Evaluation of the Severity of Aortic Stenosis

Objective: We sought to evaluate the relationship among left ventricular outflow tract diameter (LVOTd), gender, and body surface area (BSA) and to evaluate the usefulness of size-adjusted LVOTd reference values in patients with aortic stenosis (AS). AS grading is based on the echocardiographic calculation of the aortic valve area (AVA) and requires LVOTd measurements, one main potential source of error. Transesophageal echocardiography (TEE) is reputed to be more accurate than transthoracic echocardiography (TTE), but validation studies are rare. A safeguard for LVOTd measurements is thus desirable. Methods: Since January 2006, 3 subsets of patients have been prospectively and concurrently enrolled: 1) TEE group: In 120 patients with and without AS, we prospectively measured LVOTd during both TTE and TEE. 2) Validation set: In 382 patients without aortic valve or ascending aorta diseases, we evaluated the relationship among LVOTd, gender, and BSA. 3) Testing set: In 173 patients with AS, we compared the AVA obtained using measured LVOTd (AVA(MEAS)) and calculated LVOTd derived from a regression determined in the validation set (AVA(CALC)). Results: TTE did not differ from and correlated well with TEE measurements overall (23 +/- 2 mm vs 23 +/- 2 mm, P=.26; r=0.95, P<.0001) and in patients with AS (N=43) (24 +/- 2 mm vs 24 6 3 mm, P=.15; r=0.92, P<.0001). LVOTd was linearly correlated to BSA independently of gender (LVOTd=5.7 * BSA+12.1; r=0.55, P<.0001). In the testing set, AVA(CALC) did not differ from and correlated well with AVAMEAS (1.20 +/- 0.42 cm(2) vs 1.23 +/- 0.40 cm(2); P=.08; r=0.89; P<.0001). Conclusion: TTE and TEE measurements of the LVOTd provided similar results. LVOTd was significantly associated to BSA and LVOTd, derived from a linear regression linked to BSA independently of gender, provided an acceptable approximation of the AVA. Thus, although accurate measurement of LVOTd is a crucial part of the echocardiographic evaluation of AS severity, the present equation may be used as a safeguard when this measurement is difficult or not possible with TTE. (J Am Soc Echocardiogr 2009; 22: 445-451.)