Systems and methods for RF ablation using jet injection of a conductive fluid

Abstract

A method of preparing and ablating heart tissue includes a pre-treatment step of delivering a jet of conductive fluid to a portion of heart tissue. The conductive fluid is delivered using an injection device such as a hand-held jet injector, probe, or catheter. After injecting the heart tissue with the conductive fluid, RF energy is delivered to the site of the injection to form a lesion. The method enables a physician to produce large and accurately placed lesions within the treated tissue.

Description

FIELD OF THE INVENTION [0001] The present invention relates generally to the field of radio frequency (RF) ablation of tissue, and, more specifically, to devices and methods for the neddleless injection of a conductive fluid into tissue prior to and in conjunction with RF ablation. BACKGROUND OF THE INVENTION [0002] RF ablation techniques destroy tissue by heating. Typically, high frequency alternating current flows from one or more electrodes into the tissue, producing ionic agitation in the tissue about the electrode area as the ions attempt to follow the direction changes of the alternating current. The agitation eventually drives water from the cells leading to desiccation and coagulation, thereby creating a lesion in the tissue. There are generally two forms of heating that lead to lesion formation in RF ablated tissue. The first is primary heating (direct) of tissue via the interaction of the tissue with the alternating current of the RF electrode. Tissue is also heated by sec...

AI Technical Summary

Benefits of technology

[0015] It is an object of the invention to provide a method for pre-treating tissue prior to RF ablation. It is a further object of the invention to provide a method that reduces the effective resistivity of tissues and thereby reduce power dissipation in those same tissues. Another object of the invention is to provide an improved RF ablation method that can form accurate and deep lesions within tissue. Another object of the invention is to proved a combination injection device / RF ablation device. The combined device can take the form of a probe or a catheter. These and other objects of the invention are described in detail below.

Problems solved by technology

The presence of arrhythmogenic site or accessory pathway can bypass or short circuit these normal pathways, potentially resulting in very rapid heart contractions, typically referred to as tachycardias.

The maximum safe RF power that can be delivered is limited by the need to keep the maximum tissue temperature below 100° C. If tissue temperature exceeds 100° C., an explosive release of steam can erupt that could cause harmful and unwanted perforations in the tissue.

However, a disadvantage of cooling the RF electrodes is that this exterior cooling does not greatly effect tissue temperature more than about 2 mm below the surface.

While temperatures may be within acceptable limits at the surface, temperatures below the surface may exceed safety margins.

Since the hottest tissue temperatures are located 1-3 mm below the surface, control of RF power to safe levels using active cooling is difficult.

The difficulty with this method lies in the unpredictability of the fluid transfer.

Moreover, prior art devices typically delivery saline solutions at relatively low pressures, relying on the migration of the saline fluid through the extracellular space.

Consequently, it is sometimes difficult to produce deep penetration of saline solution over a specific portion of the tissue of interest.

The conductive fluid, in other words, does not reliably go in a consistent pattern thus making a predictable and precise ablation of tissue ablation very difficult.

Because of the unpredictable nature of injection of a conductive fluid via a needle, this is not an optimum approach in the treatment of a disease such as cardiac arrhythmia (i.e., in treatments where precision is important).

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