Left ventricular outflow tract

The left ventricular outflow tract, LVOT, is the passage within the left ventricle leading to the aortic valve. It links the ventricular cavity with the aortic root; the neighboring anterior mitral valve leaflet and ventricular septal structures help define this outflow region.^[ref][ref]

Its measurement is useful in Doppler echocardiography. In a fixed-area model, a cross-sectional area $A$ and area-mean axial velocity $\overline{u}(t)$ give the forward transported volumewhere the velocity-time integral has dimensions of length. It is not a peak velocity or a volume by itself. The primary technical report uses paired diameter and Doppler measurements at a consistent outflow site.^[ref]

For a stipulated circular diameter $D=2.0$ cm and velocity-time integral 20 cm,If the measured diameter is instead 2.2 cm with the same integral, the estimated area and volume both increase by $(2.2/2.0{)}^2=1.21$, or $21\%$. A $10\%$ diameter change therefore does not produce only a $10\%$ volume change.

The approximation requires consistent geometry and velocity sampling. A noncircular outline, changing area, nonuniform flow or an angled ultrasound beam can alter the relation between a measured signal and area-mean velocity. The left ventricular outflow tract also names anatomy, while aortic stenosis names a pathological narrowing at the valve: a passage's location alone does not establish whether it is obstructed.