What are the standard measurements to obtain in the parasternal long‑axis (PLAX) view of an echocardiogram, including normal reference ranges?

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PLAX View Measurements in Echocardiography

In the parasternal long-axis (PLAX) view, you should routinely measure: left ventricular internal dimensions (end-diastolic and end-systolic), interventricular septal thickness, posterior wall thickness, left atrial diameter, and aortic root dimensions at four specific levels (annulus, sinuses of Valsalva, sinotubular junction, and proximal ascending aorta). 1

Left Ventricular Linear Dimensions

The PLAX view provides critical linear measurements of the LV, though volumetric assessment is now preferred when feasible. Use 2D-guided measurements rather than M-mode for improved accuracy 1.

Standard LV Measurements:

  • LV end-diastolic dimension (LVEDD): Measured at the onset of the QRS complex or when the LV cavity is largest
  • LV end-systolic dimension (LVESD): Measured at the smallest LV cavity size, typically after aortic valve closure

Normal Reference Ranges (2D measurements):

Men:

  • LVEDD: 42.0–58.4 mm (mean 50.2 ± 4.1 mm)
  • LVESD: 25.0–39.8 mm (mean 32.4 ± 3.7 mm)

Women:

  • LVEDD: 37.8–52.2 mm (mean 45.0 ± 3.6 mm)
  • LVESD: 21.6–34.8 mm (mean 28.2 ± 3.3 mm)

1

Important Technical Note:

Recent evidence suggests that midventricular measurements (at the true maximal LV diameter) correlate better with volumetric standards than traditional basal measurements 2. However, current guidelines still recommend basal measurements for standardization. When reporting, specify the measurement level used to enable inter-study comparison 1.

Wall Thickness Measurements

Measure both walls at end-diastole in the PLAX view:

  • Interventricular septal thickness (IVS)
  • Posterior wall thickness (PW)

These measurements are essential for calculating LV mass and identifying hypertrophy patterns (concentric vs. eccentric) 3.

Aortic Root Measurements

The PLAX view is the primary window for aortic root assessment. Measure at four distinct anatomic levels 1:

  1. Aortic annulus: At the hinge points of the aortic leaflets (measure at peak systole, unlike other dimensions)
  2. Sinuses of Valsalva: At maximal diameter (typically midpoint), measured at end-diastole
  3. Sinotubular junction: Measured at end-diastole
  4. Proximal ascending aorta: Measured at end-diastole (document distance from annular plane)

Critical Technical Points:

  • The aortic root plane differs from the LV long axis—adjust transducer position accordingly
  • Ensure measurements are perpendicular to the aortic long axis
  • An asymmetric closure line of aortic leaflets indicates the cross-section is not optimal 1

Left Atrial Dimension

Measure the anteroposterior LA diameter in the PLAX view at end-systole (maximal LA size), from the posterior aortic root wall to the posterior LA wall 1.

Important caveat: LA diameter underestimates true LA size compared to volumetric methods. The 2015 ASE/EACVI guidelines recommend LA volume assessment from apical views as the preferred method, but LA diameter from PLAX remains a quick screening measurement 1.

Key Technical Considerations

Measurement Timing:

  • End-diastole: First frame after mitral valve closure OR frame with largest LV dimension
  • End-systole: Frame after aortic valve closure OR frame with smallest LV dimension
  • Use M-mode or Doppler valve clicks for precise timing in regular rhythms 1

Common Pitfalls to Avoid:

  • Oblique imaging planes: Ensure true long axis to avoid underestimating dimensions
  • Foreshortening: Maximize LV length to avoid measurement errors
  • Endocardial definition: Poor visualization of the anterior RV wall and LV endocardium can compromise accuracy
  • Trabeculations: Include in cavity measurements, not wall thickness 1

Quality Optimization:

  • Adjust depth and gain settings for optimal endocardial border visualization
  • The PLAX view should display the mitral valve leaflets, LV outflow tract, and aortic valve in a single plane
  • Consider contrast enhancement if endocardial borders are poorly defined 1

Indexing to Body Surface Area

Always report indexed values (measurements divided by BSA) in addition to absolute values, particularly for chamber dimensions and volumes. This accounts for body size variation and improves diagnostic accuracy 1.

Integration with Other Views

While PLAX provides essential linear measurements, volumetric assessment using the biplane method of disks from apical views is now the recommended standard for LV size and function 1. PLAX measurements complement but do not replace comprehensive volumetric analysis. The 2015 guidelines emphasize that linear dimensions have significant limitations in patients with regional wall motion abnormalities or asymmetric remodeling 1.

References

2
Research

Optimal Technique for Measurement of Linear Left Ventricular Dimensions.

Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography, 2019

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.