By Dr. Larry Istrail, author of The POCUS Manifesto: Expanding the limits of our physical exam with point-of-care ultrasound.
In our quest to reimagine the physical exam in the POCUS Era, we spend a lot of time thinking about how simple and quick sonographic techniques or measurements can provide us with high diagnostic accuracy.
With aortic stenosis, this is one case where we feel the stethoscope still has value when it comes to basic screening. Since the aortic stenosis murmur is so characteristic and relatively easy to appreciate, when it is heard, the specificity is high enough that it can accurately be ruled in. But if it is not heard, it cannot rule it out (not sensitive enough).
The gold standard is acquiring an apical 5-chamber view with the left ventricular outflow tract/aortic valve in view and using continuous-wave doppler to calculate a velocity. But this is an advanced technique, and the apical 4 and 5 chamber views can be quite difficult to acquire and master.
Another good option may be the Maximal Aortic Valve Cusp separation (MACS).
In a study from 2017, researchers measured aortic leaflet separation in M-mode. They defined it as the distance between the inner edges of the tips of leaflets at mid systole in the parasternal long-axis view. They then measured it with 2-D echo at mid systole and took the average. Their results were pretty excellent for an initial screening test:
They also found a nice negative correlation between the separation of the aortic leaflets and the velocity through the valve.
They concluded by saying "there was a strong correlation between aortic cuspal separation and severity of aortic stenosis. Aortic cuspal separation <8.25 mm showed a sensitivity of 89%, specificity of 94%, positive predictive value of 92%, negative predictive value of 91% and predictive accuracy of 92% in detecting severe aortic stenosis. Aortic cuspal separation ≥11.25 mm had a sensitivity of 88%, specificity of 93%, positive predictive value of 95%, negative predictive value of 82% and predictive accuracy of 92% in detecting mild aortic stenosis."
Have you ever tried this to diagnose aortic stenosis?
Get a copy of The POCUS Manifesto: Expanding the limits of our physical exam with point-of-care ultrasound.