Apparatus for forming a passageway in tissue and associated interventional medical systems

An interventional medical system comprising:

• an introducer sheath and an apparatus for forming a passageway through tissue in a body of a patient;
• the introducer sheath comprising a longitudinally extending lumen extending from a proximal opening thereof to a distal opening thereof, the lumen being sized to receive passage of the apparatus therethrough and out the distal opening thereof, the system further comprising a relatively compact implantable medical device, the medical device comprising a hermetically sealed housing and having an electrode mounted to the housing, the lumen of the introducer sheath being sized to receive passage of the device therethrough and out the distal opening thereto;
• the apparatus comprising:
• an elongate shaft extending over a length from a proximal end thereof to a distal end thereof, the shaft including a lumen extending from the proximal end to the distal end;
• a dilator mounted to the distal end of the shaft, the dilator including a proximal end, a distal end, a first portion, a second portion, and a longitudinally extending lumen, the first portion extending from the proximal end of the dilator to the second portion, the second portion extending from the first portion to the distal end of the dilator, the lumen of the dilator being in fluid communication with the lumen of the shaft and including a distal opening located at the distal end of the dilator, the second portion having a decreasing taper from the first portion to the dilator distal end, and the second portion including an external thread formed along the decreasing taper.