change value of item in BinaryHeap

["Øivind" via Digitalmars-d-learn]

I am trying to figure out how to change the value of an element 
in a BinaryHeap (from std.container) and have it repositioned 
such that the heap is still valid.

Can anyone help me with this? The approach I would have taken (I 
think) is to remove the elements that get new values from the 
heap, and simply re-insert them, but I cannot find a function 
that can allow me to remove an arbitrary element

Use-case is implementing Visvalingam's algorithm for shape 
simplification. I need to always select the element (point on 
shape) of lowest value (area between it and 2 surrounding 
points), but doing so changes the value (area) of the 2 
surrounding points, and they have to be repositioned in the heap..