How is aortic regurgitation jet length measured with Transthoracic Echocardiography (TTE)?

From the Guidelines

Aortic regurgitation jet length is measured from the vena contracta to the last pixel of regurgitant color using transthoracic echocardiography (TTE) with color Doppler imaging in multiple views, with a jet length ≥1 cm in at least one view indicating pathological aortic regurgitation. This measurement is part of a comprehensive assessment that should include other parameters such as vena contracta width, pressure half-time, and regurgitant volume for accurate grading of aortic regurgitation severity 1. The jet length assessment is valuable because it provides a quick visual estimate of regurgitation severity, though it can be influenced by technical factors such as transducer position, Doppler gain settings, and patient hemodynamics.

Some key points to consider when measuring aortic regurgitation jet length include:

• Obtaining color Doppler imaging in the parasternal long-axis or apical views
• Visualizing the regurgitant jet as a high-velocity, mosaic-colored flow moving from the aorta back into the left ventricle during diastole
• Measuring the jet length from the vena contracta to the last pixel of regurgitant color
• Expressing the measurement in centimeters or as a ratio of jet length to left ventricular outflow tract length
• Considering other parameters such as vena contracta width, pressure half-time, and regurgitant volume for accurate grading of aortic regurgitation severity 1.

It's also important to note that the color flow area of the regurgitant jet, as a single parameter, is not recommended to quantify the severity of aortic regurgitation, and a more quantitative approach is required when more than a small central AR jet is observed 1. Additionally, TTE is indicated in patients with signs or symptoms of AR for accurate diagnosis of the cause of regurgitation, regurgitant severity, and LV size and systolic function, and for determining clinical outcome and timing of valve intervention 1.

From the Research

Aortic Regurgitation Jet Length Measurement with TTE

• The measurement of aortic regurgitation jet length is an important aspect of assessing the severity of aortic regurgitation using transthoracic echocardiography (TTE) 2, 3.
• According to a study published in 1993, jet length is one of the parameters that correlates well with the severity of regurgitation as assessed by contrast aortography, with a correlation coefficient of 0.88 2.
• Another study published in 2000 found that jet width had the best correlation with angiography, but jet length was not specifically mentioned as a parameter used in the study 3.
• However, a study published in 2001 used transesophageal color Doppler imaging of the vena contracta to validate the accuracy of color flow vena contracta measurements of aortic regurgitation severity, and found that vena contracta width and area correlated well with regurgitant fraction and regurgitant volume obtained by intraoperative flow probe 4.
• It is worth noting that TTE has some limitations in assessing aortic regurgitation, and other imaging modalities such as transesophageal echocardiography (TEE) and cardiovascular magnetic resonance (CMR) may provide more accurate and prognostically relevant information 5, 6.

Parameters Used to Assess Aortic Regurgitation Severity

• Jet length and jet area are two of the parameters used to assess the severity of aortic regurgitation using TTE 2.
• Other parameters used to assess aortic regurgitation severity include the ratio of jet area to left ventricular diastolic area, the ratio of jet width to the width of the left ventricular outflow tract, and jet width 2.
• The vena contracta width and area are also used to assess aortic regurgitation severity, and have been found to correlate well with regurgitant fraction and regurgitant volume obtained by intraoperative flow probe 4.

Limitations of TTE in Assessing Aortic Regurgitation

• TTE has some limitations in assessing aortic regurgitation, including its relatively limited integrated semi-quantitative/qualitative approach 6.
• TTE may underestimate the severity of aortic regurgitation, particularly in patients with eccentric jets or concomitant aortic stenosis 3.
• Other imaging modalities such as TEE and CMR may provide more accurate and prognostically relevant information in assessing aortic regurgitation severity 5, 6.