Stylet with improved threadability

A low or non-torqueable stylet comprising:

• a core wire including:
• a first pre-formed bend of a first angle of about 15-90°;
• a second pre-formed bend of a second angle of about 8-15°, the second pre-formed bend being distal of the first pre-formed bend, and the first pre-formed bend being longer than the second pre-formed bend;
• an intermediate portion of about 1-3 inches extending between the first pre-formed bend and the second pre-formed bend;
• and
• a distal portion of about 1-2 inches between the second pre-formed bend and an end of a distal tip, the distal portion having a narrow segment with a reduced width or diameter that increases deflection of the distal tip, wherein the first pre-formed bend and the second pre-formed bend are entirely within 10 inches from an end the distal tip of the core wire;
• a navigation device disposed around the core wire;
• and
• a tubular body disposed around the core wire and the navigation device;
• wherein the core wire has a pre-formed shape including the first pre-formed bend and the second pre-formed bend, and the core wire being configured to elastically change from the pre-formed shape to a second shape during insertion of the stylet into a vasculature of the patient due to an anatomical insertion pathway of the vasculature;
• and
• wherein a distal tip of the core wire extends distally from a distal end of the tubular body, the distal tip of the core wire being exposed for conducting an electrocardiogram signal, and the distal end of the tubular body being configured to prevent fluid from entering the tubular body.