Shockwave catheter system with energy control

Inventors

Hakala, Doug • Adams, John M. • Holmberg, Randy

Assignees

Shockwave Medical Inc

Abstract

A system that breaks calcium in a liquid includes a catheter including first and second electrodes arranged to receive there-across a high electrical voltage at an initial low current. The high electrical voltage causes an electrical arc to form across the electrodes creating a gas bubble within the liquid, a high current to flow through the electrodes, and a mechanical shock wave. A power source provides the electrodes with the high electrical voltage at the initial current and terminates the high electrical voltage in response to the high current flow through the electrodes.

Core Innovation

The invention relates to a method of delivering shock waves to treat a calcified lesion in a body of a patient using a catheter. A distal portion of the catheter is adjacent to the calcified lesion, and the distal portion comprises a pair of electrodes immersed in a conductive fluid. The electrodes are connected to a power source, and the catheter is advanced through a body lumen to position the electrode pair for shock wave generation.

The method delivers a series of voltage pulses from the power source to the pair of electrodes. Each voltage pulse is generated by closing at least one switch so that charge stored on at least one capacitor is delivered to the pair of electrodes. The voltage pulse has sufficient energy to generate an arc in the conductive fluid, allowing current to flow across the electrodes to produce a shock wave.

The method includes monitoring at least one parameter of the voltage pulses and terminating delivery of each voltage pulse based on the monitored parameter reaching a predetermined value. The predetermined value ensures creation of the arc for the voltage pulse, and terminating delivery comprises opening the at least one switch to prevent a remaining charge on the capacitor from being delivered. This configuration conserves electrode material by preventing unnecessary remaining energy delivery after the predetermined condition is reached.

The disclosed system and control concepts further include energy control based on pulse monitoring and reducing energy when fluid temperature rises relative to ambient, with timing control that accounts for switch turn-off delay to reach a current peak. The shockwave behavior is discussed in terms of leading edge shock wave generation and trailing edge shock wave reliability, and the approach is described as extendable beyond a balloon, including non-balloon embodiments for stone treatment such as ureter and kidney stone.

Claims Coverage

The independent claim covers a method with four inventive elements: catheter placement with an electrode pair in conductive fluid, generation of arc-producing voltage pulses via switched capacitor discharge, monitoring of at least one pulse parameter, and per-pulse termination by switch opening to prevent remaining capacitor charge and conserve electrode material.

Overall claim coverage centers on delivering shock waves by positioning a catheter with immersed electrodes at a calcified lesion, creating arc-produced shock waves via switched, capacitor-driven voltage pulses, monitoring a pulse parameter, and terminating each pulse by switch opening when a predetermined condition is met to conserve electrode material. The document further indicates dependent refinements such as electrode placement in an angioplasty balloon, current sensing/resistor-based parameter monitoring, and additional energy reduction triggers based on fluid temperature and timing control accounting for switch turn-off delay.

Stated Advantages

Documented Applications