The article here tells that in HCM due to ventricular premature contraction there is enough time for dilatation of ventricular filling which increases end diastolic volume thereby increasing obstruction due to increase in gradient across the obstruction (Frank starling mechanism).
On the other hand when we talk about increase in preload, we say that it decreases the obstruction which can be appreciated on hearing the murmur which is of less intensity. Examples can be like in squatting and leg raising.
Aren't these two situation contradicting each other? On one hand due increase in preload there increase in obstruction causing Brockenbrough-Braunwald-Morrow sign to occur while on the other hand increase in preload decreases the intensity of murmur?
