Aortic regurgitation assessment
From Echocardiography in ICU
Acute or chronic aortic regurgitation
Aortic regurgitation (AR) may be congenital or acquired. It is important to distinguish between acute or chronic aortic regurgitation, and to assess its consequence on the left ventricle.
Acute regurgitation can be caused by:
The tolerance will depend on the amount of regurgitation, the capacity of the left ventricle to deal with acutely increased pre-load and the rapidity of installation. If there is a suspicion of aortic dissection or endocarditis, the realization of trans-esophageal echocardiography is mandatory.
Chronic regurgitation can be caused by:
-aortic calcfications with restriction of the opening and closing of the valve. It is important to look for associated aortic stenosis.
-aortic valve malformation, including bicuspid aortic valve
-aortic root and annulus dilatation (Marfan syndrome, hypertension)
Positive diagnosis of AR will be realized with color Doppler, in parasternal long axis or apical 5 or 3 chamber views. AR will appear as a diastolic jet from aorta to LV:-parasternal long axis: the regurgitant jet may be perpendicular, directed toward or away from the probe. The color coding of the jet can not be predicted, the timing of the regurgitation (holo-diastole) is the most important criteria of diagnosis of AR. On this loop you can see moderate AR directed toward the anterior leaflet of the mitral valve. There is also mild MR.
-apical 5 and 3 chamber: the regurgitant jet will appear as a yellow-red mosaic diastolic jet, coming from the aorta to the left ventricle. Continuous Doppler on the aortic valve will show holodiastolic positive flow (going from the aorta to the LV, toward the probe), at high speed: >3.5 m/s.
On this loop you can visualize moderate AR directed toward the anterior leaflet of the mitral valve:
- Visual estimation
It is difficult to assess the severity of AR, and relies mainly on visual estimation of the extension of the regurgitant jet in the left ventricle. A few indices can be used:
- Vena Contracta
In parasternal long axis, you will measure the diameter of the AR where the jet is the narrowest (through the valve). AR is considered as severe if the vena contracta diameter is > 6mm.
- Telediastolic speed at aortic isthmus
From supra-sternal incidence, with continuous Doppler on the descending aorta, below the left subclavian artery. In normal subjects, there is a systolic negative flow around 1m/s and a short proto-diastolic positive flow < 0.25m/s. A telediastolic flow > 18cm/s corresponds to regurgitant fraction > 40%, severe AR.
The consequences of AR on the left ventricle will depend on the acuteness of AR and of the LV capacity to adapt to increased volume pre-load.
In acute AR, the LV size will remain normal at the beginning, with hyperdynamic systolic function.
In chronic AR (bicuspid aortic valve, aortic root dilatation), the LV dilates to maintain adequate stroke volume. Lately, when the capacity of adaptation of the LV are exceeded, systolic LV dysfunction appears.
Touche T, Prasquier R, Nintenberg A, De Zuterre D, Gourgon R. Assessment and follow-up of patients with aortic regurgitation by an updated Doppler echocardiographic measurement of the regurgitant fraction in the aortic arch. Circulation 1985;72:819-24.