Aims: Accurate measurement of left ventricular outflow tract diameter (LVOTd) is essential for reliable estimation of aortic valve area (AVA) using the continuity equation. Transesophageal echocardiography (TEE) can accurately delineate the LVOT. The aim of this study was to assess the accuracy and reproducibility of LVOTd measurement using transthoracic echocardiography (TTE) with harmonic imaging when compared with TEE, in both systole and diastole.
Methods and results: We prospectively studied 50 patients [20 with aortic stenosis (AS) and 30 without AS]. LVOTd was measured offline in a blinded fashion in both systole and diastole by two experienced observers using TTE in the parasternal long axis view and TEE in the mid-oesophageal aortic view ( approximately 130 degrees ). There was strong correlation between TTE and TEE (r=0.91). LVOTd was slightly smaller by TTE when compared with TEE (2.11+/-0.21 vs. 2.16+/-0.22 cm, mean difference -0.05+/-0.09 cm, P=0.0003). Compared with TEE, 95% (2SD) of LVOTd measurements by TTE were within +0.14 and -0.24 cm. Inter- and intra-observer variability for LVOTd was 4.8+/-4.1 and 2.8+/-1.9% for TTE and 4.2+/-3.1 and 2.5+/-1.6% for TEE (P=0.4 and 0.6). In patients with AS, estimated AVA was 0.93+/-0.22 cm(2) using TTE and 0.96+/-0.24 cm(2) using TEE, P=0.08. Diastolic LVOTd by TEE was slightly smaller compared with systolic LVOTd by TEE (-0.03+/-0.07 cm, P=0.0005), and there was strong correlation between the two (r=0.95).
Conclusion: We present the data regarding accuracy and reproducibility of LVOTd measurements by TTE when compared with TEE. LVOTd measurements at end-diastole may be helpful when systolic images are suboptimal.