MR, LVOT and AV signal differentiation
| View | Apical CW and PW recordings; colour Doppler occasionally helps avoid an eccentric MR jet. |
|---|---|
| Timing | Compare signal duration with the ECG: ejection-only (LVOT/AV) versus mitral closure to mitral opening (MR). |
| Caliper / trace | Identify the signal before measuring: AS jet from the dense ejection envelope; LVOT from the PW gate; MR from the longer envelope spanning the isovolumic periods. |
Correct example
A systolic signal away from the apex that starts at mitral closure and continues until mitral opening is MR; the AS jet is confined to ejection. The LVOT signal is the laminar PW curve obtained with the gate on the LV side of the valve.
Common error
Measuring a high-velocity MR jet as the AS jet (both are systolic and directed away from the apex), or sampling the LVOT so close to the valve that the PW curve shows the stenotic jet.
Effect on interpretation
An MR jet mistaken for AS overestimates the gradient and underestimates AVA; in acute severe MR the curve shape can mimic AS, so timing rather than shape is the reliable discriminator.
Why
The curve shape distinguishes fixed from dynamic obstruction (late-peaking, concave-upward early systole) but not MR from AS; a faint duplicated envelope at exactly twice the modal velocity is a double-envelope artifact, not a second jet.