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Publication Date: 2009-May-18
Document File: 4 page(s) / 339K

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The Prior Art Database

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During monopolar RF ablation, heat generated by an ablation electrode is dispersed through an indifferent return pad attached to the patient’s skin.  The amount of heat dispersed through the indifferent pad is dependent upon the level of RF power used in the ablation procedure.  High-power RF ablation may cause excessive heating under the indifferent return pad and first to third degree burns on the patient’s skin. 

In addition, for electrosurgery at powers above 50 Watts, there is a requirement to demonstrate compliance with certain onerous and ever-changing FDA pre-market approval (PMA) standards.  However, if RF power can be limited to 50 Watts, RF generators and catheters are not required to demonstrate compliance with such standards.

Therefore, there is a need for an effective, efficient low-power RF ablation system.


Fig. 1 depicts the distal portion of an end or side-fire catheter 10 being used in a low-power, side-fire monopolar ablation.  The distal portion of the catheter 10 generally includes three separate electrodes – one distal tip electrode 12 and two electrodes 14 and 16 on opposing sides of the distal portion of the catheter 10.  In a monopolar ablation procedure, one of the side electrodes 16 is in contact with the target tissue 18, as shown in Fig. 1, and the RF current flows from the side electrode 16 to the dispersive indifferent pad 20 that is disposed on the external surface of the patient’s skin.  The end or side-fire catheter may similarly be used in a low-power, end-fire monopolar ablation procedure, wherein the distal tip electrode 12 is in contact with the target tissue 18.

Electrodes 12, 14 and 16 are designed such that the electrode contacting the target tissue is substantially completely embedded in the target tissue.  This will result in efficient power delivery for lesion formation.  Since the lesion-forming electrode (i.e., the electrode contacting the target tissue 18) may not be exposed to blood flow, the lesion-forming electrode may not by passively cooled by blood flow.  Thus, irrigation cooling of the electrodes 12, 14 and 16 may be required. 

The ablation system can easily detect which of the three electrodes 12, 14, 16 is contacting the target tissue 18.  RF energy is then advantageously delivered only through the electrode that is determined to be in contact with the target tissue 18.  In most cases, RF power is never delivered above 100 Watts, hence this implementation would limit the power below 25 Watts.

Limiting the RF power in this manner would cause this RF ablation system to fall out of the scope of certain FDA PMA standards that are particular to electrosurgery at powers above 50 Watts.  By eliminating the need to demonstrate compliance with s...