Echocardiographic evaluation in aortic regurgitation

Echocardiographic evaluation of aortic regurgitation, demonstrated through multiple images. Echocardiogram in parasternal long axis view shows dilated left ventricle, left atrium, aorta and a small portion of the right ventricle, which is usually the outflow region. Mitral valve leaflets seen in open position between the left ventricle and left atrium are thickened.
The large aortic regurgitation jet can be seen as a mosaic jet in the left ventricular outflow tract anterior to the anterior mitral leaflet. A portion of the thickened aortic valve can be seen between the aorta and left ventricle.
The AR jet is almost filling the left ventricular outflow tract and extends well into the left ventricle, beyond the anterior mitral leaflet, indicating a free aortic regurgitation. Dilated left ventricle, aorta and left atrium also suggest that the AR is severe.
Apical five chamber view shows the dilated left ventricle, thickened anterior mitral leaflet and posterior mitral leaflet. In this view also the AR jet is large, extending deep into the LV, indicating severe AR.
Thickening of both aortic and mitral leaflets indicate the possible etiology as rheumatic. Mitral and aortic valves are the most often involved valves in rheumatic heart disease, the former being more common between the two.
When there is associated mitral stenosis, the colour Doppler jet of mitral flow merges with that of aortic regurgitation in the left ventricle as both occur in diastole.
But the velocity of aortic regurgitation jet is much higher than that of mitral stenosis as the pressure difference between aorta and left ventricle in diastole is much higher than that between left atrium and left ventricle.
This is a parasternal long axis view from another case. Aortic valve is seen as grossly thickened and calcified. The right panel shows the multi coloured jet of aortic regurgitation along the ventricular surface of the anterior mitral leaflet. This is quite an eccentric AR jet and hence assessment of severity will be difficult.
Here is another eccentric jet of aortic regurgitation going along the posterior margin of the left ventricular outflow tract or the anterior mitral leaflet. The systolic frame on the right shows the mitral valve in the closed position while the diastolic frame on the left shows it in the open position.
The anterior mitral leaflet shows a reverse doming as the aortic regurgitation jet strikes it. Systolic frame also shows a trivial mitral regurgitation into the left atrium, just behind the mitral valve as a bluish mosaic jet.
Measurement of vena contracta or the width of the proximal regurgitant jet for grading aortic regurgitation becomes unreliable when the jet is eccentric. In central jets, a jet width less than 0.3 cm is highly specific for mild AR and a width more than 0.6 cm is highly specific for severe AR.
Here we have both continuous wave Doppler and color Doppler imaging from apical five chamber view side by side. The right panel shows continuous wave of aortic regurgitation jet. Below the baseline forward aortic flow is seen while above the baseline the tongue shaped aortic regurgitation jet is seen.
Apical five chamber view in the left panel shows colour Doppler image of aortic regurgitation with a wide multicoloured jet originating from the closed aortic valve into the left ventricle. From extent of the AR jet into the left ventricle it is moderately severe AR.
Parasternal long axis view showing a small AR jet. Such a small jet will be taken as trivial aortic regurgitation, with no hemodynamic significance. Left atrium and left ventricle are not dilated.
Trivial aortic regurgitation on Doppler interrogation from the apical five chamber view, which is seen as 2-D image in the upper panel. Incomplete image of the jet is obtained when the regurgitant flow is less as in trivial or mild AR.
The jet seen below the baseline is the forward aortic flow in systole, whereas AR occurs in diastole and is seen above the baseline. This is because the regurgitant flow into the left ventricle is towards the transducer in this view. The forward velocity is about 1.2 m/sec, indicating the absence of any associated aortic stenosis.
The colour bar on the top left indicates that the Nyquist limit of the colour Doppler imaging has been set at 60 cm/s. The scale on the left lower side is the Doppler scale in m/s, with positive values above the baseline and negative values below the baseline.
Picture demonstrates measurement of pressure half time of aortic regurgitation jet using continuous wave Doppler from the apical five chamber view. Apical five chamber view with colour Doppler is seen in the upper right corner of the of the image.
The Doppler cursor is seen passing through the left ventricular outflow tract and aorta. AR jet is seen as the positive tracing above the baseline. The peak velocity of the AR jet is shown as 4.79 m/s. AR PHT is shown as 453 ms. The AR deceleration slope is shown as 310 cm/s2.
Pressure half time is the time required for the peak pressure gradient to reduce by half which will correspond to a decrease in peak velocity by a factor of square root of two. PHT of a regurgitant jet depends on the severity of the regurgitation and the compliance of the receiving chamber.
If the compliance of the receiving chamber is low, the pressure in the receiving chamber rises rapidly and the pressure gradient decreases rapidly leading to a steep slope of the Doppler tracing and a low pressure half time. This is the usual situation in an acute regurgitation when the receiving chamber does not get much time to dilate and accommodate the regurgitant flow.
Severe regurgitation also gives a similar picture as the receiving chamber fills rapidly. PHT measurement by Doppler echocardiography is useful in assessing the severity of aortic regurgitation.
The severity of aortic regurgitation has been classified according to the pressure half time as follows: Mild AR: PHT >500 ms, Moderate AR: PHT between 200 – 500 ms, Severe AR: PHT <200 ms. As mentioned above, PHT depends on the compliance of the receiving chamber and hence it can be reduced by elevated LV diastolic pressure. On the contrary, it can be prolonged if the peripheral resistance is increased and when the aorta is dilated and having a higher compliance. Vasodilator therapy can reduce PHT in AR.