Abstract: An electrosurgical apparatus for cutting tissue and for ablating occlusions includes a pulse generator for selectively generating a train of pulses of electrical energy for application to a wire having an attached electrode, the generator having a variable output impedance, the wire and the electrode being at least part of a load impedance. The apparatus senses the load impedance relative to the output impedance and adjusts the output impedance to match the load impedance. The generator produces pulses of variable energy, measures the relative electrical energy produced by an arc in response to a pulse, compares the relative electrical energy to a predetermined value to determine an energy difference, and adjusts the energy of a subsequent pulse to reduce the energy difference for the subsequent pulse toward zero.