Determining aortic stenosis severity: what to do when measuring left ventricular outflow tract diameter is difficult.

Contemporary decision-making in aortic stenosis (AS) is based on clinical assessment in conjunction with echocardiographic determination of AS severity and left ventricular ejection fraction. The primary hemodynamic parameters recommended for clinical evaluation of valvular AS are AS peak jet velocity, mean transaortic gradient, and aortic valve area (AVA) by continuity equation. Each of these measures has limitations, and it is essential to integrate all Doppler and two-dimensional echocardiographic data to determine AS severity accurately. AVA determined by the continuity equation has the advantage of being less flow dependent than the other parameters. For a reliable estimation of the AVA (or more accurately, the effective orifice area [EOA]), an accurate estimate of stroke volume must be obtained. In current practice, this depends on the ability to determine a left ventricular outflow tract (LVOT) area. This in turn depends on the assumption of a circular (or cylindrical) LVOT shape, in conjunction with the ability to obtain an accurate linear LVOT diameter (LVOTd). The LVOT area should be determined at a location within the LVOT that closely corresponds to the region where a technically adequate pulsed-wave Doppler signal is obtained. Because the linear dimension (LVOTd) is squared to obtain LVOT area, it is easy to see how the inability to measure the LVOT diameter accurately remains the Achilles’ heel of this technique. So how should AVA be determined when the LVOTd cannot be accurately measured? The careful study by Leye et al presented in this issue of the Journal seeks to address this conundrum. The authors are to be congratulated on performing a large study with both validation and test populations. In the validation cohort, the authors explore the relationship among LVOTd, gender, height, and body surface area (BSA). By using an LVOTd derived from the BSA, they determined AVA in their test population (AVAcalc) and compared it with AVA determined using a measured LVOTd (AVAmeasured), along conventional lines. The authors found that LVOTd was significantly larger in men (24 6 4 mm) than in women (21 6 2 mm; P < .0001) but was not significantly different between genders after indexation to BSA (12.4 6 1.2 in men vs 12.6 6 1.4 mm/m in women, P = .26). After indexation to height, LVOTd was significantly different between genders (1.36 6 0.1 in men vs 1.31 6 0.1 in women, P < .0001). On the basis of their findings, the authors proposed that LVOTd