An apparatus for forming a passageway through tissue includes a dilator mounted to a shaft, wherein the dilator includes a first portion, which has an increasing taper from a first outer diameter to a larger second outer diameter, and a second portion, which has a decreasing taper from the first portion to a distal end of the dilator, and which includes an external non-cutting thread formed along the decreasing taper. Lumens of the dilator and shaft provide a conduit for means to pierce through the tissue, for example, an elongate wire that includes a piercing tip. In some cases, the dilator first portion is expandable to, and contractible from, the larger second outer diameter, wherein the apparatus may include a spreading member configured to slide between the shaft and the first portion. The apparatus may be included in a system with an introducer sheath.