Piercing the skin of the chest was a way of "deflating" the bloated vampire; this is similar to the act of burying sharp objects, such as sickles, in with the corpse, so that they may penetrate the skin if the body bloats sufficiently while transforming into a revenant.
In one striking example of the latter, the corpses of five people in graveyard near Polish village of Dravsko dating from the 17th and 18th centuries were buried with sickles placed around their necks or across their abdomens