"The stiff Heart questions" in Dickinson's "After great pain"

The third line of Emily Dickinson's "After great pain, a formal feeling comes" does not settle into the steady iambic pentameter the second line seems to have established but returns to a variation on the stress pattern of the first line: "The stiff Heart questions" does not reproduce the initial troche of line one, but the second foot is again a spondee. The heart's questioning is thus linked to the "great pain" of the first line: it may come after that pain, as the "formal feeling" does in general, but that feeling has to return to the form it first gave to the pain in order to formulate its "stiff questions". (Andrew Shields, #111words, 27 May)