A catheter apparatus of the type used in the treatment of heart arrhythmia comprising: - a catheter shaft having a main body extending along a central axis and a coaxial tip section joined to the main body, the tip section having a tip distal end and being rotatable about the central axis and deflectable such that the tip section can be selectively curved away from the central axis; - a mapping and ablation catheter slidably disposed within the catheter shaft, the mapping and ablation catheter having a catheter distal portion, the catheter distal portion being a pre-stressed curve whereby the mapping and ablation catheter curves as the catheter distal portion is extended axially from the catheter shaft and when the catheter distal portion is fully extended from the catheter shaft, all of the curve is substantially coplanar with a plane substantially perpendicular to the central axis at the tip distal end; and - a control mechanism coupled to both the catheter shaft and the mapping and ablation catheter whereby the control mechanism controls, with respect to the central axis, selective rotation and selective deflection of the tip section and controls selective axial movement of the mapping and ablation catheter with respect to the catheter shaft; and wherein the mapping and ablation catheter forms a loop when the mapping and ablation catheter is fully extended from the catheter shaft; and wherein: - the control mechanism is a steering handle; - the steering handle has a first actuator mechanically connected with respect to the catheter shaft whereby actuation of the first actuator can independently rotate the tip section about the central axis and deflect the tip section away from the central axis, wherein the tip section can deflect 180° to the right and to the left of the central axis within a plane coplanar with the central axis; and - the steering handle has a second actuator mechanically connected with respect to the mapping and ablation catheter whereby actuation of the second actuator can independently move the mapping and ablation catheter axially within the catheter shaft and control the diameter of the loop formed by the mapping and ablation catheter. - a catheter shaft having a main body extending along a central axis and a coaxial tip section joined to the main body, the tip section having a tip distal end and being rotatable about the central axis and deflectable such that the tip section can be selectively curved away from the central axis; - a mapping and ablation catheter slidably disposed within the catheter shaft, the mapping and ablation catheter having a catheter distal portion, the catheter distal portion being a pre-stressed curve whereby the mapping and ablation catheter curves as the catheter distal portion is extended axially from the catheter shaft and when the catheter distal portion is fully extended from the catheter shaft, all of the curve is substantially coplanar with a plane substantially perpendicular to the central axis at the tip distal end; and - a control mechanism coupled to both the catheter shaft and the mapping and ablation catheter whereby the control mechanism controls, with respect to the central axis, selective rotation and selective deflection of the tip section and controls selective axial movement of the mapping and ablation catheter with respect to the catheter shaft; and wherein - the control mechanism is a steering handle; - the steering handle has a first actuator mechanically connected with respect to the catheter shaft whereby actuation of the first actuator can independently rotate the tip section about the central axis and deflect the tip section away from the central axis, wherein the tip section can deflect 180° to the right and to the left of the central axis within a plane coplanar with the central axis; and - the steering handle has a second actuator mechanically connected with respect to the mapping and ablation catheter whereby actuation of the second actuator can independently move the mapping and ablation catheter axially within the catheter shaft and control the diameter of the loop formed by the mapping and ablation catheter.