The psion can use Transmassion to separate an object into multiple parts. A living victim opposes the power as usual (thanks to his psi aura, biological template, noetic register - whatever you like to call it), reducing the damage the psion can inflict.
Even so, almost any successful attack cripples its target in some particular. Bear in mind that the psion must see or otherwise accurately sense the target; a subject’s heart isn’t appreciably different from the rest of his internal organs as far as Spatial Sense is concerned. It’s worth noting that this has many useful applications to inanimate objects as well; it’s not purely a destructive technique.