A translatable shock wave treatment apparatus is suitable for use in treating calcified lesions in vascular structures having small diameters. An elongate member carrying a collapsed angioplasty balloon is first inserted into the occluded blood vessel. The angioplasty balloon is inflated with a conducting fluid to pre-dilate the narrow blood vessel prior to introducing electrodes and applying shock wave therapy. After the blood vessel is at least partially opened, a translatable electrode carrier equipped with one or more shock wave emitters is advanced into the angioplasty balloon. Shock waves are then propagated through the fluid to impart energy to calcified plaques along the vessel walls, thereby softening the calcified lesions. Following the shock wave treatment, multiple inflation and deflation cycles of the angioplasty balloon can be administered to gently compress the softened lesion and complete dilation of the blood vessel.