What is the normal left ventricular outflow tract (LVOT) diameter?

From the Guidelines

The normal left ventricular outflow tract (LVOT) diameter is approximately 1.8 cm, as measured in the parasternal long-axis view during echocardiography, at the level of the aortic annulus, according to the European Association of Cardiovascular Imaging and the American Society of Echocardiography 1.

Key Considerations for LVOT Diameter Measurement

• The measurement should be taken in mid-systole, when the outflow tract is at its maximum diameter, to ensure accuracy in calculating cardiac output and assessing aortic stenosis severity 1.
• The LVOT diameter can be measured at the annulus level or within 0.3–1.0 cm of the valve orifice, with some experts preferring one method over the other, but the annulus level offers higher measurement reproducibility and easier correlation with transcatheter valve sizing 1.
• Challenges in measurement include calcium extension from the aortic annulus to the base of the anterior mitral leaflet, which can yield an incorrectly small LVOT diameter, and the presence of a ‘sigmoid septum’, where the LVOT diameter measured apically from the annulus may appear smaller than the flow area at the annulus 1.
• The assumption of a circular shape of the LVOT may lead to underestimation of LVOT CSA and, consequently, underestimation of stroke volume (SV) and aortic valve area (AVA), as the LVOT is often elliptical rather than circular 1.

Clinical Implications

• Accurate measurement of the LVOT diameter is crucial because small errors can significantly impact derived calculations, such as aortic valve area, due to the squaring of the LVOT diameter in these formulas 1.
• Variations in LVOT diameter can occur based on body size, gender, and age, with larger individuals generally having larger measurements, emphasizing the need for personalized assessment 1.
• Abnormal narrowing of the LVOT may indicate conditions such as hypertrophic cardiomyopathy or subaortic stenosis, highlighting the importance of precise measurement and interpretation in clinical practice 1.

From the Research

Normal LVOT Diameter

The normal left ventricular outflow tract (LVOT) diameter can vary depending on several factors, including body surface area (BSA) and gender.

• According to a study published in 2009 2, the LVOT diameter was linearly correlated to BSA, with a mean diameter of 23 +/- 2 mm.
• Another study published in 2021 3 found that the 2D LVOT diameter was larger than the 3D LVOT diameter, with a mean diameter of 2.12 cm before cardiopulmonary bypass and 1.96 cm after cardiopulmonary bypass.
• A study published in 2012 4 found that the normal LVOT area indexed to body surface area was 2.3 +/- 0.5 cm(2)/m(2) in women and 2.6 +/- 0.7 cm(2)/m(2) in men.
• The same study 4 also found that the LVOT was ovoid in shape, with a larger transverse diameter than anterior-posterior diameter during diastole and systole.

Factors Affecting LVOT Diameter

Several factors can affect the LVOT diameter, including:

• Body surface area (BSA): The LVOT diameter is linearly correlated to BSA, with larger diameters found in individuals with larger BSA 2.
• Gender: Men tend to have larger LVOT diameters than women 4.
• Cardiopulmonary bypass: The LVOT diameter can decrease after cardiopulmonary bypass 3.
• Aortic stenosis: Patients with aortic stenosis tend to have smaller LVOT diameters than those without the condition 3.

Measurement of LVOT Diameter

The measurement of LVOT diameter can be done using various imaging modalities, including:

• Transthoracic echocardiography (TTE): TTE can provide accurate measurements of LVOT diameter, with a mean diameter of 23 +/- 2 mm 2.
• Transesophageal echocardiography (TEE): TEE can also provide accurate measurements of LVOT diameter, with a mean diameter of 23 +/- 2 mm 2.
• Three-dimensional transesophageal echocardiography: This modality can provide more accurate measurements of LVOT diameter and area than 2D imaging 3.
• Cardiac computed tomographic angiography: This modality can provide clear definition of the LVOT and accurate measurements of LVOT diameter and area 4.
• The location of LVOT measurement is also important, with a study published in 2025 5 finding that measurements taken at 3 mm from the annulus most closely agreed with gold standard cardiac magnetic resonance imaging (CMR) SV.