A first catheter is dimensioned for deployment within a renal artery. A second catheter has a shaft with an outer diameter smaller than an inner diameter of the first catheters open lumen. A gap is formed between the shaft and the first catheter when the second catheter is situated within the first catheter. The gap facilitates transport of a fluid, such as imaging contrast media, along the first catheter. An electrode arrangement at the distal end of the shaft is configured to deliver ablative energy to perivascular renal nerves, and has an outer diameter about the same size as the inner diameter of the first catheter such that a fit therebetween substantially blocks fluid flow within the gap yet provides for relative movement between the electrode arrangement and the luminal wall. A conductor extends between the proximal and distal ends of the shaft and is coupled to electrode arrangement.
