A medical device may include an elongated body, a balloon positioned at a distal portion of the elongated body, and one or more pressure-wave emitters positioned along a central longitudinal axis of the elongated body within the balloon. The one or more pressure-wave emitters may be configured to propagate pressure waves radially outward through the fluid to fragment a calcified lesion at the target treatment site. The at least one of the one or more pressure-wave emitters may comprise an electronic emitter including a first electrode and a second electrode. The first electrode and the second electrode may be arranged to define a spark gap between the first electrode and the second electrode, and the second electrode may comprise a portion of a hypotube.