a low profile defibrillation catheter is disclosed which is much thinner than existing devices . the thin structure is provided by using the current conductor coil as a first electrode coil and the same materials as the conductor for the second electrode . the second electrode coil is bonded to the second conductor coil and wound in the same direction . the thin design is motivated by an electrical field analysis which reveals that the length of the catheter is the important determinant of defibrillation efficacy , and that the large radius and surface area of prior art devices were less beneficial .