Surgery – Instruments – Electrical application
Reexamination Certificate
2002-04-15
2004-06-29
Gibson, Roy D. (Department: 3735)
Surgery
Instruments
Electrical application
C128S898000
Reexamination Certificate
active
06755824
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to an electrophysiological (“EP”) catheter for providing energy to biological tissue within a biological site, and more particularly, to an EP catheter with a platelet inhibitor substance stored therein that becomes eluted upon contact with biological fluid and thereby prevents the formation of coagulum and other substances from adhering to the catheter surface during an ablation procedure.
2. Description of the Related Art
The heart beat in a healthy human is controlled by the sinoatrial node (“S-A node”) located in the wall of the right atrium. The S-A node generates electrical signal potentials that are transmitted through pathways of conductive heart tissue in the atrium to the atrioventricular node (“A-V node”) which in turn transmits the electrical signals throughout the ventricle by means of the His and Purkinje conductive tissues. Improper growth, remodeling, or damage to, the conductive tissue in the heart can interfere with the passage of regular electrical signals from the S-A and A-V nodes. Electrical signal irregularities resulting from such interference can disturb the normal rhythm of the heart and cause an abnormal rhythmic condition referred to as “cardiac arrhythmia.”
While there are different treatments for cardiac arrhythmia, including the application of anti-arrhythmia drugs, in many cases ablation of the damaged tissue can restore the correct operation of the heart. Such ablation can be performed percutaneously, a procedure in which a catheter is introduced into the patient through an artery or vein and directed to the atrium or ventricle of the heart to perform single or multiple diagnostic, therapeutic, and/or surgical procedures. In such case, an ablation procedure is used to destroy the tissue causing the arrhythmia in an attempt to remove the electrical signal irregularities or create a conductive tissue block to restore normal heart beat. Successful ablation of the conductive tissue at the arrhythmia initiation site usually terminates the arrhythmia or at least moderates the heart rhythm to acceptable levels. A widely accepted treatment for arrhythmia involves the application of RF energy to the conductive tissue.
In the case of atrial fibrillation (“AF”), a procedure published by Cox et al. and known as the “Maze procedure” involves the formation of continuous atrial incisions to prevent atrial reentry and to allow sinus impulses to activate the entire myocardium. While this procedure has been found to be successful, it involves an intensely invasive approach. It is more desirable to accomplish the same result as the Maze procedure by use of a less invasive approach, such as through the use of an appropriate EP catheter system providing RF ablation therapy. In this therapy, transmural ablation lesions are formed in the atria to prevent atrial reentry and to allow sinus impulses to activate the entire myocardium. In this sense transmural is meant to include lesions that pass through the atrial wall or ventricle wall from the interior surface (endocardium) to the exterior surface (epicardium).
During ablation, RF energy is applied to the electrodes to raise the temperature of the target tissue to a lethal, non-viable state. In general, the lethal temperature boundary between viable and non-viable tissue is between approximately 45° C. to 55° C. and more specifically, approximately 48° C. Tissue heated to a temperature above 48° C. for several seconds becomes permanently non-viable and defines the ablation volume. Tissue adjacent to the electrodes delivering RF energy is heated by resistive heating which is conducted radially outward from the electrode-tissue interface. The goal is to elevate the tissue temperature, which is generally at 37° C., fairly uniformly to an ablation temperature above 48° C., while keeping both the temperature at the tissue surface and the temperature of the electrode below 100° C. In clinical applications, the target temperature is set below 70° C. to avoid coagulum formation. Lesion size has been demonstrated to be proportional to temperature.
Blood coagulation is a major limitation/complication associated with RF ablation therapy. Coagulation can lead to thromboembolism and can also form an insulating layer around the electrode hindering further energy delivery required for ablation therapy. Heat appears to be a major factor in the formation of blood coagulum on a catheter electrode. During a typical RF energy ablation procedure using an EP catheter, on or more electrodes carried by the catheter are positioned such that a portion of the electrodes are in contact with the tissue being ablated while the remaining portion of the electrodes are in contact with blood. The RF energy applied during the procedure resistively heats the tissue which in turn heats the electrode through conduction. As blood stays in contact with the heated electrode, platelet activation occurs. This platelet activation appears to lead to coagulum formation.
Hence, those skilled in the art have recognized a need for providing a catheter with a platelet inhibitor substance dispersed therein that becomes eluted upon contact with biological fluid and thereby prevents the formation of coagulum and other substances from adhering to the catheter surface during an ablation procedure. The invention fulfills these needs and others.
SUMMARY OF THE INVENTION
Briefly, and in general terms, the invention is directed to an ablation catheter having a platelet inhibitor substance dispersed therein that becomes eluted upon contact with biological fluid and thereby prevents the formation of coagulum and other substances from adhering to the catheter surface during an ablation procedure.
In a first aspect, the invention relates to a catheter for use within a body cavity having biological fluid therein. The catheter includes a shaft having a proximal end, a distal-end region and an outside surface. At least one pocket is carried by the shaft and has an opening terminating at the outside surface of the shaft. The catheter also includes a soluble platelet inhibitor substance within the at least one pocket that is adapted to pass through the pocket opening upon contact with the biological fluid. By incorporating a platelet inhibitor substance within the pocket opening for the subsequent elution thereof, adhesion of blood platelets on the surface of the catheter is prevented or at least substantially minimized. Accordingly, coagulum causing components of the blood cannot contact the catheter surface and coagulation cannot begin and hence, not propagate.
In a detailed aspect, the platelet inhibitor includes heparin, glycoprotein IIb/IIIa inhibitor and aspirin. In another detailed aspect, the shaft has a tubular wall which carries the at least one pocket. In yet another detailed aspect, the at least one pocket is within the tubular wall. In a further detailed aspect, the at least one pocket is within the lumen defined by the tubular wall. In another detailed aspect, the shaft further includes at least one electrode that carries the at least one pocket. In other detailed aspects, a layer of a platelet inhibitor substance is posited on an outside surface of the shaft. Alternatively, a layer of a heparin and sugar-based solution mixture is deposited over the outside surface of the shaft with the layer adapted to dissolve into the biological fluid. In a further detailed aspect, the solubility of the platelet inhibitor substance increases with temperature through application of RF energy by an RF generator to the catheter surface.
In a second aspect, the invention relates to a catheter system for use within a body cavity. The catheter system includes a shaft having a proximal end and a distal-end region. The shaft carries a lumen network having a proximal opening that communicates with a source of platelet inhibitor solution and at least one distal opening that is adapted to terminate at the outside surface of the shaft. The catheter system further includes a first mechanism adapted to force the
Hall Jeffrey A.
Jain Mudit K.
KenKnight Bruce
Morris Milton M.
Walcott Gregory P.
Gibson Roy D.
Myers Bigel & Sibley & Sajovec
UAB Research Foundation
Vrettakos Peter J
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