Mastering LVOT Obstruction Assessment: A Step-by-Step Approach
How to Spot Systolic Anterior Motion (SAM) Every Time
What is an LVOT Obstruction?
A dynamic left ventricular outflow tract (LVOT) obstruction occurs when blood leaving the left ventricle is forced through a narrowed pathway before entering the aorta. This can happen at the valvular, subvalvular, or supravalvular level—and echocardiography is the frontline tool for pinpointing both the location and severity of obstruction, at both rest and with a Valsalva maneuver.
Here’s the catch: the most common culprit isn’t the aortic valve—it’s systolic anterior motion (SAM) of the mitral valve, especially in hypertrophic cardiomyopathy cases. And if your Doppler protocol isn’t dialed in, you’ll underestimate—or miss—the gradient.
Inside today’s lesson, you’ll learn:
The step-by-step Doppler workflow (2D → Color → PW → CW) to confirm dynamic LVOT obstruction
The mechanism behind obstruction and what to look for on TTE exams
5 proven steps to sharpen your SAM assessment
How to separate MR from true obstruction and capture the highest pressure gradient
Provocation strategies (Valsalva, positioning), beat selection, and gradient measurement tips
Case clips with window-by-window breakdowns
Why Does This Matter?
Any obstruction to forward flow alters intracardiac pressures—leading to increased afterload, hypertrophy, cavity dilation, and, if left untreated, progression to heart failure.
Hypertrophic cardiomyopathy, which affects about 1 in 500 individuals according to the CDC, is a prime example. These cases demand special attention to the mitral valve morphology.
2D Findings
At the beginning of a TTE protocol, systolic anterior motion can easily be missed with two dimensional imaging alone. We have to remember that there are two types of systolic anterior motion (SAM) to look out for during our protocols. Both can cause a dynamic LVOT obstruction with high velocities on Doppler, but chordal SAM often produces a less severe obstruction and may be trickier to recognize.
Leaflet SAM = anterior mitral leaflet moves into the LVOT.
Chordal SAM = chordae tendineae move into the LVOT.