Left Ventricular Outflow Geometry in Aortic Stenosis

Objective: to characterize left ventricular outflow tract (LVOT) morphometry at different levels during systole(S) and diastole(D). Accurate LVOT area measurement is crucial for correct calculation of the aortic valve area by the continuity method, but correct LVOT transection level is controversial, performed inconsistently at different institutions at the aortic annulus or 5-10mm below it.

Methods: 30 patients with severe aortic stenosis underwent TEE and CT assessment pre-trans-aortic valvular intervention at the aortic annulus level (LVOT0), 5mm below (LVOT1) and 10mm below (LVOT2). 3D-TEE image-cropping was used to measure LVOT dimensions (area by planimetry, ellipticity index(EI)=maximal/minimal diameter ratio). Measurements were compared with LVOT0 by CT (best spatial resolution).

Results: 30 patients (18 females) aged 81±8 years were studied. As shown in Figure, CT-LVOT0[3.9(3.5-2.9)cm2, median(IQR)] was higher than TEE-LVOT0[3.3(2.9-4.1)cm2], p<0.05. LVOT0 [3.45(2.9-4.3)cm2] was similar to LVOT1 [3.44(2.9-4.18cm2)] with LVOT2 significantly higher 3.7(2.8-4.5)cm2, p<0.05]. LVOT areas decreased significantly in diastole. EI was smaller at LVOT0 by TEE compared with CT [1.15(1.1-1.2) vs 1.3(1.2-1.4) respectively, p<0.05], with progressive increase with increasing distance from the annulus reaching 1.38(1.31-1.1.44) at LVOT2. EI at LVOT0 by CT was similar to EI at LVOT1 by TEE. Significantly further deformation is noted in diastole, up to 1.74(1.61-2.0.7) at LVOT2.

Conclusions: LVOT area should be measured at the aortic annulus or 5 mm below. The LVOT becomes more elliptical with increasing distance from the annulus.