How can you differentiate between LVOT obstruction and mitral regurgitation on Doppler?

To differentiate between left ventricular outflow tract (LVOT) obstruction and mitral regurgitation using Doppler ultrasound, timing within the cardiac cycle is a pivotal factor. The hemodynamic profiles of these two conditions are distinct regarding when the abnormal flow occurs.

In the case of LVOT obstruction, typically caused by conditions such as hypertrophic cardiomyopathy, the obstruction leads to a dynamic change in the outflow during systole. The Doppler signal for LVOT obstruction is prominently observed during the systolic phase when the ventricle is contracting and the aortic valve is opening, resulting in a sharp increase in flow velocity just after the ventricle begins to eject blood.

Conversely, mitral regurgitation results in backflow from the left ventricle into the left atrium during systole when the mitral valve should be closed. The Doppler signal in mitral regurgitation shows a continuous turbulent flow pattern that begins when the ventricle contracts and persists for the duration of systole.

By carefully assessing the timing of the Doppler signals throughout the cardiac cycle, a sonographer can distinguish between these two conditions: sharp peaks during systole indicating LVOT obstruction versus a more prolonged flow pattern suggesting mitral regurg