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

From the Guidelines

Aortic regurgitation jet height is measured using transthoracic echocardiography (TTE) by obtaining a parasternal long-axis view of the left ventricular outflow tract and aortic valve, with the measurement taken at the vena contracta, which is the narrowest portion of the regurgitant jet, and a VC width of <3 mm correlates with mild AR, whereas a width >6 mm indicates severe AR, as per the recommendations from the European Association of Cardiovascular Imaging 1. The regurgitant jet is visualized using color Doppler imaging, and its height is measured at the level of the left ventricular outflow tract, just below the aortic valve. The ratio of the jet height to the left ventricular outflow tract height is then calculated, with a ratio greater than 65% suggesting severe aortic regurgitation. For accurate measurements, the color Doppler scale should be optimized to avoid overestimation or underestimation of the jet, typically using a Nyquist limit of 50-60 cm/s, as recommended in the guidelines for the echocardiographic assessment of native valvular regurgitation 1. Multiple measurements from different cardiac cycles should be averaged for better accuracy. This method is valuable because the vena contracta represents the actual regurgitant orifice area and correlates well with the severity of aortic regurgitation, though it should be interpreted alongside other parameters such as pressure half-time, regurgitant volume, and left ventricular dimensions for comprehensive assessment. Some key points to consider when measuring aortic regurgitation jet height include:

• Optimizing colour gain/scale in parasternal long- and short-axis views
• Identifying the three components of the regurgitant jet (VC, PISA, jet into LV)
• Reducing the colour sector size and imaging depth to maximize frame rate
• Expanding the selected zone (Zoom) and using the cine-loop to find the best frame for measurement
• Measuring the smallest VC (immediately distal to the regurgitant orifice, perpendicular to the direction of the jet), as outlined in the guidelines for echocardiographic assessment of native valvular regurgitation 1.

From the Research

Measurement of Aortic Regurgitation Jet Height with TTE

• The height of the regurgitant jet relative to left ventricular outflow tract height measured from the parasternal long-axis view just beneath the aortic valve can be used to assess aortic regurgitation severity, correctly classifying 23 of the 29 patients 2.
• The ratio of maximal jet height to left ventricular outflow tract height is also a useful parameter, with a good correlation between color Doppler and aortography 3.
• The maximal length and area of the regurgitant jet are poorly predictive of the angiographic grade of aortic insufficiency 2.
• The short-axis area of the regurgitant jet from the parasternal short-axis view at the level of the high left ventricular outflow tract relative to the short-axis area of the left ventricular outflow tract at the same location can also predict angiographic grade 2.

Comparison with Other Methods

• Transthoracic echocardiography (TTE) and intraoperative transesophageal echocardiography (TEE) have modest agreement in assessing aortic regurgitation severity, with TEE tend to grade AR as more severe 4.
• Vena contracta width and area measured by TEE color flow mapping are accurate markers of aortic regurgitation severity, correlating well with regurgitant fraction and regurgitant volume obtained by intraoperative flow probe 5.

Limitations and Variability

• There is considerable overlap of color Doppler grades in patients with mild aortic regurgitation, making it difficult to distinguish among milder grades 3.
• Blood pressure differences between preoperative TTE and prepump TEE do not significantly correlate with valvular regurgitation severity 4.