Moffitt Morning Report: Low flow, low gradient severe aortic stenosis!

Happy Tues, Moffitt!

Thanks to Lily for presenting a very interesting case of a middle-aged woman with CAD, HFrEF, PAH, low-flow, low-gradient severe AS, mod MR/TR, and ESRD who was transferred from an OSH with cardiogenic shock. We talked about how to diagnose severe AS and also got an opportunity to learn about low-flow, low-gradient severe AS. See pearls below and awesome review article that Lily provided attached!

 TLC (Tim and Laura, your Chiefs)

 

Diagnostic criteria for degree of aortic stenosis

As we reviewed this morning, there are several diagnostic criteria for how to categorize aortic stenosis based on the flow gradient across the valve and the measured valve area on echo. I made a table to summarize our discussion:

  Mild AS Moderate AS Severe AS
Peak aortic velosity (m/s) 2.0-2.9 3.0-3.9 >4.0
Mean gradient (mmHg) <25 25-40 >40
Aortic valve area (cm2) >1.5 1.0-1.5 <1.0

 

  • KEY POINT: Severe AS = mean gradient >40mmHg and aortic valve area <1cm2.
  • Triad of symptoms of AS: Syncope, heart failure, angina
  • Significant risk factors for AS: Bicuspid aortic valve, rheumatic heart disease

 

What is low-flow, low-gradient  severe AS?

  • However, given that the gradients are a squared function of flow, even a modest decrease in flow may lead to an important reduction in gradient. These patients can have severe AS by valve area but may have normal gradients and normal AS as occurred in our patient this morning (remember her valve area was <1cm2 but her mean gradient was 25mmHg which falls into the moderate category above. In the literature, they call these patients “Low-flow, low-gradient (LF-LG) severe AS”).
  • Why does this happen? Typically, these patients have a dilated LV with markedly decreased LV systolic function, most often due to ischemic heart disease and/or to afterload mismatch
  • Sometimes for these patients it can be useful to re-calculate valve area and pressure gradients during exercise or during dobutamine stress test to see how valve areas and cardiac outputs change
  • Prognosis is usually poor (survival rate <50% at 3yr follow-up) if treated medically, but operative risk is high (6-33%) if treated surgically

Source: Pibarot, Philippe, and Jean G. Dumesnil. “Low-flow, low-gradient aortic stenosis with normal and depressed left ventricular ejection fraction.” Journal of the American College of Cardiology 60.19 (2012): 1845-1853.

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