a tubular guidewire sheath defining a plurality of lumens, the plurality of lumens comprising a first lumen for carrying a guidewire;

a shock wave generator located near a distal end of the catheter, said shock wave generator including at least one distal electrode pair, with electrodes of each pair being spaced apart to define at least one gap;

a first wire and a second wire, wherein proximal ends of the first wire and the second wire are connectable to a pulsed voltage source, and wherein distal ends of the first wire and the second wire are connected to the at least one distal electrode pair such that when high voltage pulses are applied across the first wire and the second wire, current flows across the at least one gap creating shock waves for treating an occlusion; and

a flexible cap formed from a material having elastomeric properties and sealably attached to the distal end of the catheter and surrounding the at least one distal electrode pair, said flexible cap being inflatable with conductive fluid such that the flexible cap expands to provide a space between an inner wall of the flexible cap and the at least one distal electrode pair and wherein when the flexible cap is in a deflated state, a surface area of the flexible cap is small enough that the flexible cap is not folded when the catheter is advanced into a blood vessel and when the flexible cap is in an inflated state a maximum diameter of the flexible cap is no more than 15% greater than a diameter of the flexible cap in the deflated state, with the maximum diameter of the flexible cap being independent of a size of the blood vessel, and wherein after being deflated, the flexible cap returns to a low profile configuration without folds.