Degenerative Aortic stenosis occur with either normal or congenitally malformed/ bicuspid valve.This contributes to the major chunk of aortic valve surgeries and interventions (TAVR) in elderly population . The optimal timing of aortic valve replacement in patients with AS is debatable inspite of well formed guidelines.
Three factors determine it .Symptoms , severity of aortic valve narrowing and the tactness of LV function .The last parameter is a tricky one .We used to think in the past , severe LV dysfunction is a contraindication to aortic valve surgery. Now we realise ,however severe the LV dysfunction may be , relieving the obstruction will benefit the patient and the LV function is also likely to improve.
Cardiac physicians face a dilemma when confronted with a patient with low gradient and severe LV dysfunction .In this situation they are advised to do doubtamine stress Echo and watch for the gradient .If the gradient increases that would imply true fixed stenosis . (In pseudo aortic stenosis increased contractility opens the aortic valve and gradient will fall )
While this concept appears simple .There are few important issues that goes unaddressed as we have not yet fully understood the mechanism of LV dysfunction in aortic stenosis .(Link to mechansim of LV dysfunction in Aortic stenosis.)
At what degree of aortic stenosis LV goes down fighting and fail to generate the required gradient ?
Myocardial function and behaviour at times of hemodynamic stress can be highly variable and most of us believe it is determined primarily by the genetic switches of myosin and other contractile elements .This is naturally proven at times of hypertensive left ventricular failure (Only in a fraction of the hypertensive population LV is set to fail when BP acutely raises.)
Proposed concept
Considering the complexities in cardiac mechanics , hemodynamics (and not to forget the vast control exhibited by genetic imprints over the hemodynamic behavior of LV) , it seems highly plausible even mild degrees of Aortic stenosis can inflict significant myocardial dysfunction in certain patients . Hence the phenomenon of pseudo aortic stenosis needs further critical analysis If this is proven to be true there could be a realistic indication for aortic valve intervention even in patient with low gradient / true Mild AS with LV dysfunction.
A word of caution is required .Relying too much (Which we often do ) on gradients in the assessment of aortic stenosis has skewed our common sense. Its wiser to have a meaningful look at the valve morphology . A normal appearing valve in 2D can never cause significant stenosis. Pressure recovery phenomenon also is to be given due respect as it over estimates gradient .This will effectively avoid surprises and guilt on table when we find a relatively good looking valve posted for AVR /TAVI
Dr.S.Venkatesan MD 