A catheter comprising a length of tubing, suitable for insertion into hollow viscous organs, a plurality of electrodes each having an annular side surface and a through-bore extending through the electrodes at least one spacer made being made of an insulating material, the at least one spacer spacing apart the electrodes from one another the at least one spacer including a through-bore being aligned with the through-bores in the electrodes and leads extending through the electrode and spacer through-bores, the leads connected to corresponding electrodes.
