Objective: Due to its circular shape, the area of the proximal left ventricular tract (PLVOT) adjacent to aortic valve can be derived from a single linear diameter. This is also the location of flow acceleration (FA) during systole and pulse wave Doppler (PWD) sample volume in the PLVOT can lead to overestimation of velocity (V1) and the aortic valve area (AVA). Therefore, it is recommended to derive V1 from a region of laminar flow in the elliptical shaped distal LVOT(DLVOT). Besides being inconsistent with the assumptions of continuity equation (CE), spatial difference in location of flow and area measurement can result in an inaccurate AVA by CE. We evaluated the impact of FA in the PLVOT on the accuracy of AVA by continuity-equation (CE) in patients with aortic stenosis (AS).
Methods: AVA was calculated in patients with AS with CE once with PWD derived velocity time integral (VTI) in the DLVOT (VTILVOT) and then in the PLVOT to obtain a FA velocity profile (FA-VTILVOT) for each patient. A paired sample T-TEST (p<0.05) was conducted to compare the impact of FA-VTILVOT and VTILVOT on the calculation of AVA.
Result: There were 46 patients in the study. There was a 30.3% increase in the peak FA-VTILVOT as compared to the peak VTILVOT and AVA obtained by FA-VTILVOT was 29.1% higher than obtained by VTILVOT.
Conclusion: Accuracy of AVA can be significantly impacted by the FA in the PLVOT. LVOT area should be measured with 3D imaging in the DLVOT.