Shock wave device with polarity switching
Described here are devices and methods for forming shock waves. The devices may comprise an axially extending elongate member. A first electrode pair may comprise a first electrode and a second electrode. The first electrode pair may be provided on the elongate member and positioned within a conductive fluid. A controller may be coupled to the first electrode pair. The controller may be configured to deliver a series of individual pulses to the first electrode pair, where each pulse creates a shock wave. The controller may cause current to flow through the electrode pair in a first direction for some of the pulses in the series and in a second direction opposite the first direction for the remaining pulses in the series.
1. A shock wave device comprising: an axially extending elongate member configured to be advanced through a blood vessel to treat a calcified lesion; a first electrode assembly comprising a first electrode pair and a second electrode pair, wherein the first electrode assembly is carried by the elongate member and positioned within a conductive fluid; and a controller coupled to the first electrode assembly, wherein the controller is configured to deliver a series of individual voltage pulses to the first electrode assembly such that each of the voltage pulses creates a shock wave in the conductive fluid to treat the calcified lesion, wherein the controller includes a voltage source having a constant polarity followed by a voltage polarity switch for switching the polarity of the voltage source and causing current to flow through the first electrode assembly in a first direction for some of the pulses in the series and in a second direction opposite the first direction for the remaining pulses in the series and wherein the voltage polarity switch only operates between the delivery of individual voltage pulses so each voltage pulse delivered to the first electrode assembly has a single direction of current flow wherein a first electrode in each of the first and second electrode pairs is coupled to the voltage polarity switch and wherein the second electrode in the first electrode pair is coupled to the second electrode of the second electrode pair and wherein the first electrode in each of the first and second electrode pairs has a surface area smaller than a surface area of the associated second electrode in the first and second electrode pairs.
2. The device of claim 1 wherein the voltage polarity switch causes the current to flow in the second direction for between twenty five percent and fifty percent of the pulses in the series.
3. The device of claim 1 wherein a first wire connects the first electrode of the first electrode pair to a first terminal of the voltage polarity switch, and a second wire connects the first electrode of the second electrode pair to a second terminal of the voltage polarity switch.
4. The device of claim 1 further comprising a second electrode assembly coupled in series to the first electrode assembly, the second electrode assembly including a third electrode pair and a fourth electrode pair.
5. The device of claim 4 wherein a first electrode in the third electrode pair is connected to the first electrode of the second electrode pair, and a first electrode in the fourth electrode pair is coupled to the voltage polarity switch and wherein the second electrode of the third electrode pair is coupled to the second electrode of the fourth electrode pair and wherein the first electrode in each of the third and fourth electrode pairs has a surface area smaller than a surface area of the associated second electrodes in the third and fourth electrode pairs.
6. The device of claim 5 wherein a first wire connects the first electrode of the first electrode pair to a first terminal of the voltage polarity switch, a second wire connects the first electrode of the second electrode pair to the first electrode of the third electrode pair, and a third wire connects the first electrode of the fourth electrode pair to a second terminal of the voltage polarity switch.
7. The device of claim 1 further comprising a second electrode assembly, wherein the controller comprises a multiplexer configured to selectively deliver the series of pulses to the first electrode assembly and the second electrode assembly.
8. The device of claim 1 further comprising a fluid enclosure surrounding the first electrode assembly.
9. The device of claim 8 wherein the fluid enclosure comprises a balloon surrounding a portion of the elongate member, wherein the balloon is configured to be filled with the conductive fluid, and wherein the first electrode assembly is enclosed within and spaced from the balloon.