A catheter apparatus is provided for use in the treatment of heart arrhythmia having a catheter shaft, a mapping and ablation catheter disposed within the shaft, and a control mechanism coupled to both the shaft and the catheter. The catheter shaft includes a main body and a coaxial tip section joined to the main body. The tip section can be rotated about a central axis and curved in a controlled manner. The mapping and ablation catheter can be extended outward to take the form of a pre-stressed curve. The control mechanism controls axial rotation of the tip section, the degree of deflection of the tip and longitudinal movement of the mapping and ablation catheter.
