A catheter adapted for use in a tubular region of the heart, has a catheter body, a deflectable intermediate section and a distal a mapping assembly that has a generally circular portion adapted to sit on or in a tubular region of the heart. A control handle of the catheter allows for deflection of the catheter via a first and second puller wire responsive to a deflection assembly and manipulation of distal assembly via a third puller wire responsive to a linear motion actuator assembly. The linear motion actuator assembly includes a pair of user interface knobs, a body to which a proximal end of the third puller wire anchored, and a pair of arms that movably suspends the body and transmits longitudinal travel of the knobs to the body in a manner that multiples the travel of the body relative to the travel of the knobs.