A method is disclosed for treating calcified lesions within a wall of a blood vessel. The first step includes breaking apart a calcified lesion using a plurality of shockwaves generated in an angioplasty balloon of an angioplasty catheter device. The angioplasty balloon is dilated via a fluid to a first extent to fit against at least a portion of the wall of the blood vessel. A plurality of electrical pulses are delivered to a pair of electrodes disposed within the fluid inside the balloon. The electrical pulses have an amplitude sufficient to create plasma arcs in the fluid to generate shockwaves that are conducted through the fluid and through the balloon to the blood vessel, to crack the calcified lesion. After breaking apart the calcified lesion, the angioplasty balloon is allowed to further expand to a second extent greater than the first extent, thereby expanding an opening in the blood vessel.