How to measure LVOT VTI

LVOT VTI is the distance blood travels out of the left ventricle with each beat. Multiply it by the area of the outflow tract and you have stroke volume. Here is how to get a clean signal, what the number means and where it goes wrong.

By James Napolitano. Cutoffs from the guidelines cited below.

Get the view

1. Start in the apical 4-chamber view, patient in left lateral decubitus, apex at the top center of the screen.
2. Tilt the beam anteriorly (drop the tail of the probe toward the bed) until the LVOT and aortic valve open in the middle of the screen. This is the apical 5-chamber view.
3. Turn on color. Systolic flow leaving through the LVOT is blue, away from the probe.

Place the gate

Put a PW gate in the LVOT about 0.5 to 1 cm below the aortic valve, in line with the flow. Keep the angle between the beam and the flow under 20°. Doppler reads velocity times the cosine of that angle, so an angled beam always reads low.

• At or past the valve the velocity is higher and you see the opening and closing clicks. That overestimates stroke volume. Back the gate toward the apex.
• Too deep in the LV flow has not accelerated into the outflow tract yet. The velocity and VTI read low.
• On mitral inflow the signal is above the baseline in diastole. That is the wrong flow. The LVOT is just to the left of the mitral valve in this view.

Trace the VTI

Freeze and trace the outer edge of the dense part of one beat's envelope, from the start of ejection back to the baseline. The machine integrates velocity over time and reports the VTI in cm. Average three beats in sinus rhythm and more in atrial fibrillation. Sweep speed 50 to 100 mm/s.

Normal values

Mean LVOT VTI is about 20 ± 3 cm (17 to 23 cm) at a normal heart rate. In studies, a VTI under 10 cm in acute decompensated heart failure and under 15 cm in acute pulmonary embolism was associated with worse outcomes.¹

Stroke volume and cardiac output

Measure the LVOT diameter in the parasternal long axis, inner edge to inner edge, in mid-systole. The diameter is squared, so a 1 mm error there matters more than anything else in the calculation. Many clinicians follow VTI alone over time for this reason.

Passive leg raise

Lifting the legs shifts venous blood into the chest as a reversible fluid challenge. In spontaneously breathing patients, a rise in stroke volume of 12.5% or more after passive leg raise predicted a 15% or greater rise after volume expansion (sensitivity 77%, specificity 100%).² Measure VTI at baseline and about one minute into the leg raise with the same view and gate position.³

Common mistakes

• Beam more than 20° off the flow.
• Gate at the valve, or deep in the LV.
• Tracing the faint outer feathering instead of the dense envelope.
• Measuring the LVOT diameter at a different level than the gate.

More guides

• How to measure TAPSE
• E/e′: how to measure it
• How to estimate RVSP
• The 2025 ASE diastolic function algorithm
• Tamponade: Doppler inflow variation

References

1. Blanco P. Rationale for using the velocity-time integral and the minute distance for assessing the stroke volume and cardiac output in point-of-care settings. Ultrasound J. 2020;12:21.
2. Lamia B, Ochagavia A, Monnet X, et al. Echocardiographic prediction of volume responsiveness in critically ill patients with spontaneously breathing activity. Intensive Care Med. 2007;33:1125-1132.
3. Monnet X, Marik P, Teboul JL. Passive leg raising for predicting fluid responsiveness: a systematic review and meta-analysis. Intensive Care Med. 2016;42:1935-1947.
4. Mitchell C, et al. Guidelines for performing a comprehensive transthoracic echocardiographic examination in adults: recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr. 2019;32:1-64.