Aortic stenosis is diagnosed by 2D valve morphology, area ,and pressure gradient across the aortic valve.Though anatomical 2D images and indices are good enough to diagnose severe AS , we are obsessed * with pressures which are subjected moment to moment hemodynamic and contractile variables. To record a good gradient we need a normally contracting ventricle and good flow across the narrowed LVOT. If any one of the is critically compromised gradients can’t be picked up by Doppler.(A new entity of AS was recently included , which fails to generate the gradient in spite of good LV function and the AS being significant.)
So ,whenever one records a “Low gradient AS” there are 4 distinct possibilities.
- Truly mild AS
- Technical inadequate Doppler alignment , with possible true moderate /severe anatomical AS .
- Low gradient AS due to LV dysfunction, with true moderate /severe anatomical AS
- Low gradient AS with Low flow but normal LV function, with true anatomically moderate/severe AS
Echocardiographer should rule out 1 and 2 before going to the complex world of low gradient severe AS.In my personal opinion , the entity of Low flow , Low gradient with Normal LV function appear redundant ( or is it beyond my understanding ) .One should look at the valve morphology and decide in such situations.
Then , one will shortly bump into this query is it 2 or 4 ?
How to differentiate a technically defective recording of low gradient AS from true low flow due to narrowed LVOT.(Low gradient for me , high gradient for my professor !)
Now, basic readers may please leave ,
Few inquisitive may ask ( naturally though)
Does the ” low flow -low gradient AS” is an exclusive phenomenon that can occur only with normal LV function or can it occur in dysfunctional left ventricle as well , who also have small cavity size and narrow LVOT ? (Within the low gradient AS due to LV dysfunction subset , How much is attributable due to anatomial low flow and how much is related to depressed LV contractile force ?)
Another googly . . .
Why can’t Doubutamine* stress test routinely undertaken in the subset of patients with with subjects with Low gradient /normal LV function to augment the anatomical low flow and find whether it is true low flow or not ? *This would mean , a most impractical situation wherein every patient with even mild AS should need to undergo dobutamine testing to rule out significant AS.
As of now ,this new concept “Low flow , Low gradient, with Normal LV function” appears an intellectual excess with little impact on patient outcome.The proposed new entity ultimately increase the likelyhood of over diagnosing severe AS.Iam still expecting more clarity on the issue. ( or else for the moment forget the pressures and simply fall back on a meticulous assessment of 2D valve morphology and take a call , you will be surprised how often we get into man made scientific traps. )