Stroke Volume Measurement in 2D Echocardiography
Stroke volume in 2D echocardiography is measured using the left ventricular outflow tract (LVOT) Doppler method, which multiplies the LVOT cross-sectional area by the LVOT velocity-time integral (VTI). 1
Primary Recommended Method: LVOT Doppler Technique
The standard approach involves two key measurements 1, 2:
Measure the LVOT diameter in mid-systole from the parasternal long-axis view, positioning calipers inner-edge to inner-edge at or immediately below the mitral valve leaflet tips 1
Calculate the LVOT cross-sectional area using the formula: CSA = π × (LVOT diameter)² / 4 2
Obtain the LVOT VTI using pulsed-wave Doppler with the sample volume positioned approximately 0.5 cm proximal to the aortic valve, tracing the Doppler flow signal contour 2
Calculate stroke volume as: Stroke Volume = LVOT CSA × LVOT VTI 1, 2
Alternative Volumetric Method
When the LVOT Doppler method is not feasible, stroke volume can be calculated from ventricular volumes 1:
Measure LV end-diastolic volume (EDV) and end-systolic volume (ESV) using the biplane method of disks summation (modified Simpson's rule) from apical four-chamber and two-chamber views 1
Calculate stroke volume as: SV = EDV - ESV 1
This method requires careful avoidance of foreshortening and accurate endocardial border tracing 1
Critical Technical Considerations
Proper Doppler beam alignment is essential to avoid underestimating VTI and therefore stroke volume 2. The LVOT is often elliptical rather than circular, and using only the sagittal diameter (which is typically smaller than the coronal diameter) will underestimate the LVOT area and consequently stroke volume 1.
Contrast agents should be used when two or more contiguous LV endocardial segments are poorly visualized in apical views, as contrast-enhanced images provide volumes closer to cardiac magnetic resonance measurements 1
Accuracy Hierarchy
Recent validation studies demonstrate that 3:
- LVOT Doppler with 3D LVOT area measurement provides the closest agreement with cardiac magnetic resonance (bias of 6.35%) 3
- LVOT Doppler with 2D area has greater underestimation (bias of 15.1%) 3
- 2D volumetric methods show the largest underestimation (bias of 18.3%) 3
Common Pitfalls to Avoid
Do not use the Teichholz or Quinones methods for calculating LV volumes from linear dimensions, as these rely on geometric assumptions that do not apply in various cardiac pathologies 1
Avoid measuring LVOT diameter from M-mode alone without 2D guidance, as this increases the risk of oblique sections 1
Ensure proper timing definitions: end-diastole is the first frame after mitral valve closure or when LV dimension is largest; end-systole is the frame after aortic valve closure or when dimension is smallest 1