A stylet assembly comprising a hollow transseptal cardiac needle where the hollow transseptal cardiac needle has a tip comprising: an inner surface of the hollow needle tip; an outer surface of the hollow needle tip, where the hollow needle tip has a longitudinal axis and a leading edge of the needle tip, where the leading edge of the needle tip is located at and adjacent to a distal end of the inner surface, and where the leading edge of the needle tip is located away from the outer surface, where the leading edge is angled relative to the longitudinal axis of the needle tip to define an opening of the needle tip, to define a front of the needle tip toward which the opening of the leading edge is oriented and to define a back of the needle tip opposing the front of the needle tip, where the distal end of the needle tip is curved away from the back of the needle tip toward the opening of the needle tip, the stylet assembly further comprising; a stylet including an elongate stylet body for extending the hollow transseptal cardiac needle into a predetermined position on a septal wall having an intermediate portion and a distal atraumatic portion; and a spring mechanism coupled to the elongate stylet body such that the spring mechanism is loaded when the elongate stylet body is advanced against the predetermined position on a septal wall, and where the spring mechanism is unloaded after the hollow needle assembly penetrates the septal wall allowing the elongate distal atraumatic portion to extend unsupported and thereby assume an atraumatic configuration, wherein the spring mechanism comprises: an outer housing; a concentrically included inner slidable housing, where the elongate stylet body is coupled to the inner housing; an arcuate slot (100, 112) defined in the inner housing; a slidable pin (98, 118) fixed to the outer housing and slidingly disposed in the slot so that relative position of the inner housing and elongate stylet body with respect to the outer housing is selectively controlled according to the configuration of the arcuate slot; a spring captured within the outer housing and extended between the outer and inner housings. an inner surface of the hollow needle tip; an outer surface of the hollow needle tip, where the hollow needle tip has a longitudinal axis and a leading edge of the needle tip, where the leading edge of the needle tip is located at and adjacent to a distal end of the inner surface, and where the leading edge of the needle tip is located away from the outer surface, where the leading edge is angled relative to the longitudinal axis of the needle tip to define an opening of the needle tip, to define a front of the needle tip toward which the opening of the leading edge is oriented and to define a back of the needle tip opposing the front of the needle tip, where the distal end of the needle tip is curved away from the back of the needle tip toward the opening of the needle tip, the stylet assembly further comprising; a stylet including an elongate stylet body for extending the hollow transseptal cardiac needle into a predetermined position on a septal wall having an intermediate portion and a distal atraumatic portion; and a spring mechanism coupled to the elongate stylet body such that the spring mechanism is loaded when the elongate stylet body is advanced against the predetermined position on a septal wall, and where the spring mechanism is unloaded after the hollow needle assembly penetrates the septal wall allowing the elongate distal atraumatic portion to extend unsupported and thereby assume an atraumatic configuration, wherein the spring mechanism comprises: an outer housing; a concentrically included inner slidable housing, where the elongate stylet body is coupled to the inner housing; an arcuate slot (100, 112) defined in the inner housing; a slidable pin (98, 118) fixed to the outer housing and slidingly disposed in the slot so that relative position of the inner housing and elongate stylet body with respect to the outer housing is selectively controlled according to the configuration of the arcuate slot; a spring captured within the outer housing and extended between the outer and inner housings. an outer housing; a concentrically included inner slidable housing, where the elongate stylet body is coupled to the inner housing; an arcuate slot (100, 112) defined in the inner housing; a slidable pin (98, 118) fixed to the outer housing and slidingly disposed in the slot so that relative position of the inner housing and elongate stylet body with respect to the outer housing is selectively controlled according to the configuration of the arcuate slot; a spring captured within the outer housing and extended between the outer and inner housings.