Deflectable catheter systems, apparatuses and methods utilizing thermal expansion to influence catheter deflection. A representative embodiment includes a catheter having one or more pull wires or other tensioning elements. One end of the tensioning element(s) is connected at a distal portion of the catheter to facilitate shaft deflection upon pulling the tensioning element(s). A heat-sensitive control member(s) is coupled to a proximal portion of the tensioning element(s). The elongate tensioning element(s) is pulled in a proximal direction to deflect the distal portion of the catheter in response to a temperature change applied to the heat-sensitive control member.