Importance

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Abstract

A cryocatheter for treatment of tissue has a tip adapted to provide a signal indicative of the quality and/or orientation of the tip contact with surrounding tissue. In one embodiment, a signal conductor extends through the catheter to the tip and connects to a thermally and electrically conductive shell or cap that applies an RF current to the region of tissue contacted by the tip. The tissue impedance path between the signal lead and a surface electrode mounted on the patient's skin is monitored to develop a quantitative measure of tissue contact at the distal tip, which is preferably displayed on the screen of a catheter monitoring console. In yet a further embodiment, the catheter is provided with a split tip having temperature monitoring sensors, such as thermistors, mounted on opposed halves of the tip so as to sense temperature on two sides of the catheter axis. The thermistor signals are processed to determine and display differential temperature between the two sides of the tip, thus revealing which side lies in contact. In yet a further aspect of the first embodiment, two separate and distinct high frequency electrical signals are applied to the two halves of a split metal shell or cap at the tip. Signals received at the surface electrode are filtered into first and second frequency components, and these are processed to determine the relative magnitude of the signal or the impedance of the path for each of the injected signals to determine and display the tissue contact orientation of the catheter. The catheter preferably has two separate cooling chambers within the cooling tip, positioned with one chamber on each side of the axis, and a separate cooling inlet to each chamber is switched on by a valve which directs the flow of coolant to the contact side during active cryotreatment. In another embodiment, the cap provides an RF electrode that may be opposed to the cooling side so that either the cryogenic or the RF ablation side may be rotated into contact to selectively heat or cool, or in representative protocol treat, then thaw, the same tissue site.

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First Claim