Precision electrode movement control for renal nerve ablation

A catheter is configured to access a renal artery. A lumen of the catheter's shaft is dimensioned to receive a flexible actuation member which extends between the shaft's proximal and distal ends. The actuation member is moveable within the lumen and subject to elastic deformation, friction, and/or whip along its length. A flexible support member is coupled to a distal end of the actuation member and extendible beyond a distal tip of the shaft. An RF ablation electrode at a distal end of the support member is configured to ablated perivascular renal nerve tissue. A position converter at the distal end of the shaft is configured to convert movement of the actuation member into one or both of controlled rotational and axial movement of the support member and electrode to one of a multiplicity of stable circumferential positions substantially free of elastic deformation, friction, and/or whip impacting actuation member movement.