Calculate cardiac output from Doppler echocardiography using LVOT VTI and diameter. Includes stroke volume, cardiac index, and SV index.
Doppler echocardiography provides a non-invasive way to estimate cardiac output (CO) from LVOT flow measurements. The approach relies on measuring blood flow velocity through the left ventricular outflow tract (LVOT) and integrating that velocity over time to obtain the velocity-time integral (VTI).
The stroke volume (SV) is calculated as the product of the LVOT cross-sectional area and the LVOT VTI. The LVOT diameter is measured in the parasternal long-axis view during mid-systole, and the VTI is obtained from a pulsed-wave Doppler sample placed just proximal to the aortic valve in the apical 5-chamber view. Cardiac output is then SV × heart rate.
This method is commonly used in echocardiography labs and ICU hemodynamic assessment. Because the LVOT diameter is squared in the area calculation, even small measurement errors in diameter lead to larger errors in the final result — so measurement technique matters. Serial measurements using LVOT VTI alone (without re-measuring diameter) are particularly useful for tracking trends, as VTI change directly reflects stroke volume change.
Doppler echocardiographic cardiac output measurement is a widely available non-invasive hemodynamic technique. It is useful for reviewing heart failure severity, guiding fluid management, and assessing valvular disease without treating the number as a stand-alone diagnosis.
LVOT Area = π × (LVOT Diameter / 2)². Stroke Volume (SV) = LVOT Area × VTI. Cardiac Output (CO) = SV × HR / 1000. Cardiac Index (CI) = CO / BSA. SV Index (SVI) = SV / BSA.
Result: 4.85 L/min
With LVOT diameter 2.1 cm (area = 3.46 cm²), VTI 20 cm, and HR 70 bpm, stroke volume is 69.3 mL and cardiac output is 4.85 L/min (CI 2.55 L/min/m²).
Treat the LVOT diameter as the most sensitive measurement in the calculation, because the area term is squared. If you are tracking serial change, reuse the same diameter and focus on VTI change to reduce avoidable measurement noise.
Do not mix measurements from different views or heart rates without noting the clinical context. In atrial fibrillation, averaging multiple beats is usually more reliable than relying on a single cycle.
This calculator is most useful when you want to compare hemodynamics over time. A stable LVOT diameter with changing VTI usually tells the story more clearly than remeasuring everything from scratch.
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This page estimates stroke volume from LVOT diameter and VTI, then multiplies by heart rate to estimate cardiac output and indexed values. It is a worksheet-style educational tool for reviewing Doppler measurements, not a replacement for an interpreted echocardiogram or ICU assessment.
When performed properly, Doppler echocardiographic CO measurements correlate well with invasive methods. The main source of error is LVOT diameter measurement, because diameter is squared in the calculation.
Normal LVOT VTI is 18–22 cm. Values below 18 cm may suggest reduced stroke volume, while higher values can be seen in athletic hearts or high-output states.
Because LVOT area = π × (d/2)², a 1 mm error in diameter measurement results in a meaningful error in the calculated area and all derived values. Small diameter errors amplify through the area calculation, which is why consistent technique matters.
Yes. If LVOT diameter is assumed constant, serial VTI measurements directly reflect changes in stroke volume. This is commonly used in ICU settings for fluid responsiveness assessment.
In atrial fibrillation, stroke volume varies beat to beat. Average 5–10 consecutive beats to get a reliable mean VTI and calculated CO.
Yes, as long as VTI is measured proximal to the aortic valve (in the LVOT, not across the stenotic valve). The continuity equation uses this same principle to calculate aortic valve area.