AV Vmax: peak aortic velocity; AV Vmean: mean aortic velocity; AV maxPG: peak aortic gradient; AV mean PG: mean aortic gradient; AV VTI: aortic velocity time integral; AV Env.Ti: aortic velocity envelope time; HR: heart rate
Doppler echocardiography in aortic stenosis is usually done from apical five chamber (apical 5C) view. It can be done from suprasternal view as well. When dedicated continuous wave Doppler pencil probes were used, the window of choice was suprasternal.
Grading of aortic stenosis according to peak velocity
Peak aortic velocities less than 2.5 m/s are considered to be due to aortic sclerosis without significant stenosis. Mild aortic stenosis has a peak velocity between 2.5 m/s to 3 m/s. Velocity above 4 m/s is seen in severe aortic stenosis and those between 3-4 m/s in moderate aortic stenosis .
Grading of aortic stenosis according to mean gradient
Classification of aortic stenosis by mean gradient is as follows: mean gradient less than 20 mm Hg is graded as mild, 20-40 as moderate and above 40 mm Hg as severe aortic stenosis .
In the image shown above, the peak velocity is 3.03 m/s and 18.8 mm Hg. By mean gradient it is mild aortic stenosis and by peak velocity it is moderate aortic stenosis! We might as well report it as mild-moderate aortic stenosis!
The image shows and aortic regurgitation (AR) jet which is above the baseline. But the measurements of the AR jet are not shown here.
Aortic velocity time integral
Aortic velocity time integral (AV VTI) is automatically displayed by the software when the aortic velocity Doppler tracing is manually traced during measurement of peak and mean gradients. Velocity time integral is useful in calculating the aortic valve area by continuity equation. Aortic valve area by continuity equation is calculated as follows:
Aortic valve area = π*(LVOT diameter/2)2*LVOT VTI divided by aortic VTI
Continuity equation is based on the law of conservation of mass – what comes in must go out. Initial part of the formula calculates the area of the left ventricular outflow tract (LVOT) from the measured diameter of the LVOT. It is multiplied by LVOT VTI to give volume flow. It is divided by aortic VTI to get aortic valve area. Aortic valve area can be indexed by dividing with calculated body surface area. Body surface area can be calculated if height and weight are available.
Grading of aortic stenosis by valve area
Normal aortic valve area is 3-4 sq cm. If it is reduced, but above 1.5 sq cm, it is graded as mild aortic stenosis. 1-1.5 sq cm is graded as moderate and less than 1 sq cm as severe aortic stenosis.
According to body surface area, aortic valve area index of more than 0.85 will be mild aortic stenosis and index below 0.6 severe aortic stenosis. Moderate aortic stenosis has an aortic valve area index between 0.6 and 0.85.
Messika-Zeitoun D, Lloyd G. Aortic valve stenosis: evaluation and management of patients with discordant grading. E-Journal of Cardiology Practice. Vol. 15, N° 26 – 10 Jan 2018.